Update TagKeys to support purpose and purposeData

[nickjacques]

This PR adds the additional properties purpose and purposeData to the google_tags_tag_key resource. These additional properties enable the ability to deploy Secure Tags, which can then be used by Firewall Policies.

Since both purpose and purpose_data cannot be modified once set, both resources have input: true set in their definitions. Additionally, the ignore_read override is set on purpose_data. This is because although purpose_data can accept input such as the following:
- {network = "[project-id]/[vpc-name]}
- {network = "[project-id]/[vpc-id]"}
- {network = "https://www.googleapis.com/compute/v1/projects/[project-id]/global/networks/[vpc-id]"}

The API's response is always stored in the state as {network = "https://www.googleapis.com/compute/v1/projects/[project-id]/global/networks/[vpc-id]"} (also known as selfLinkWithId). As a result, persistent diffs would be generated without ignore_read, which stores the user input instead of the API's response. The API does validate that the referenced network (VPC) exists and is accessible, so using the ignore_read override will not result in a corrupted or broken state.

If this PR is for Terraform, I acknowledge that I have:

• Searched through the issue tracker for an open issue that this either resolves or contributes to, commented on it to claim it, and written "fixes {url}" or "part of {url}" in this PR description. If there were no relevant open issues, I opened one and commented that I would like to work on it (not necessary for very small changes).
• Generated Terraform, and ran make test and make lint to ensure it passes unit and linter tests.
• Ensured that all new fields I added that can be set by a user appear in at least one example (for generated resources) or third_party test (for handwritten resources or update tests).
• Ran relevant acceptance tests (If the acceptance tests do not yet pass or you are unable to run them, please let your reviewer know).
• Read the Release Notes Guide before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

tags: Added `purpose` and `purpose_data` properties to `google_tags_tag_key`

[modular-magician]

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[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 3 files changed, 113 insertions(+), 11 deletions(-))
Terraform Beta: Diff ( 3 files changed, 113 insertions(+), 11 deletions(-))
TF Validator: Diff ( 2 files changed, 3 insertions(+), 3 deletions(-))

[modular-magician]

Tests analytics

Total tests: 2176
Passed tests 1893
Skipped tests: 238
Failed tests: 45

Action taken

Triggering VCR tests in RECORDING mode for the tests that failed during VCR. Click here to see the failed tests

TestAccTags|TestAccComputeRoute_routeIlbVipExample|TestAccComputeRoute_routeIlbExample|TestAccComputeRegionNetworkEndpointGroup_regionNetworkEndpointGroupPscServiceAttachmentExample|TestAccComputePacketMirroring_computePacketMirroringFullExample|TestAccComputeInstance_soleTenantNodeAffinities|TestAccComputeManagedSslCertificate_managedSslCertificateBasicExample|TestAccFirebaserulesRelease_BasicRelease|TestAccComputeForwardingRule_serviceDirectoryRegistrations|TestAccComputeForwardingRule_networkTier|TestAccComputeForwardingRule_update|TestAccComputeForwardingRule_forwardingRuleRegionalHttpXlbExample|TestAccComputeGlobalForwardingRule_internalLoadBalancing|TestAccComputeGlobalForwardingRule_labels|TestAccComputeGlobalForwardingRule_ipv6|TestAccComputeGlobalForwardingRule_updateTarget|TestAccComputeGlobalForwardingRule_privateServiceConnectGoogleApisExample|TestAccComputeGlobalForwardingRule_globalForwardingRuleHybridExample|TestAccComputeServiceAttachment_serviceAttachmentBasicExample|TestAccComputeForwardingRule_forwardingRuleBasicExample|TestAccComputeGlobalForwardingRule_globalForwardingRuleInternalExample|TestAccComputeGlobalForwardingRule_globalForwardingRuleHttpExample|TestAccComputeGlobalForwardingRule_externalTcpProxyLbMigBackendExample|TestAccComputeVpnTunnel_regionFromGateway|TestAccComputeRouterInterface_withTunnel|TestAccComputeVpnTunnel_vpnTunnelBetaExample|TestAccComputeVpnTunnel_router|TestAccComputeForwardingRule_forwardingRuleExternallbExample|TestAccComputeForwardingRule_internalTcpUdpLbWithMigBackendExample|TestAccComputeRouterInterface_basic|TestAccComputeForwardingRule_internalHttpLbWithMigBackendExample|TestAccClouddeployDeliveryPipeline_DeliveryPipeline|TestAccComputeRouterPeer_bfd|TestAccComputeRouterPeer_enable|TestAccComputeRouterPeer_advertiseMode|TestAccComputeRouterPeer_basic|TestAccCloudRunService_cloudRunServiceMultipleRegionsExample|TestAccCGCSnippet_eventarcWorkflowsExample|TestAccClouddeployTarget_Target|TestAccDataSourceGoogleForwardingRule|TestAccDataSourceGoogleGlobalForwardingRule|TestAccComputeFirewallPolicyRule_multipleRules|TestAccComputeFirewallPolicyRule_update|TestAccComputeFirewallPolicyAssociation_basic|TestAccComputeFirewallPolicy_update

[modular-magician]

Tests passed during RECORDING mode:
TestAccTags[Debug log]
TestAccComputeRoute_routeIlbVipExample[Debug log]
TestAccComputeRoute_routeIlbExample[Debug log]
TestAccComputePacketMirroring_computePacketMirroringFullExample[Debug log]
TestAccFirebaserulesRelease_BasicRelease[Debug log]
TestAccComputeForwardingRule_serviceDirectoryRegistrations[Debug log]
TestAccComputeForwardingRule_update[Debug log]
TestAccComputeGlobalForwardingRule_internalLoadBalancing[Debug log]
TestAccComputeGlobalForwardingRule_labels[Debug log]
TestAccComputeGlobalForwardingRule_ipv6[Debug log]
TestAccComputeGlobalForwardingRule_updateTarget[Debug log]
TestAccComputeGlobalForwardingRule_privateServiceConnectGoogleApisExample[Debug log]
TestAccComputeGlobalForwardingRule_globalForwardingRuleHybridExample[Debug log]
TestAccComputeServiceAttachment_serviceAttachmentBasicExample[Debug log]
TestAccComputeGlobalForwardingRule_globalForwardingRuleInternalExample[Debug log]
TestAccComputeVpnTunnel_regionFromGateway[Debug log]
TestAccComputeForwardingRule_internalHttpLbWithMigBackendExample[Debug log]

Tests failed during RECORDING mode:
TestAccComputeInstance_soleTenantNodeAffinities[Error message] [Debug log]
TestAccComputeRouterPeer_enable[Error message] [Debug log]
TestAccComputeRouterPeer_advertiseMode[Error message] [Debug log]
TestAccCGCSnippet_eventarcWorkflowsExample[Error message] [Debug log]

Please fix these to complete your PR
View the build log or the debug log for each test

[melinath]

LGTM