Add decoder after OperationWaitTimeWithResponse

[emilymye]

Since #3085 hasn't been added to a release yet, I'm going to exclude the release note, but this should fix an issue with post-create read of AccessContextManager service perimeter resource

(fixes hashicorp/terraform-provider-google#5704)

Release Note Template for Downstream PRs (will be copied)

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 34 files changed, 210 insertions(+), 66 deletions(-))
Terraform Beta: Diff ( 40 files changed, 234 insertions(+), 68 deletions(-))

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 15 files changed, 47 insertions(+), 15 deletions(-))
Terraform Beta: Diff ( 17 files changed, 61 insertions(+), 17 deletions(-))

[emilymye]

Looks like the Spanner decoder might not be necessary after this change? I'll test that in a different PR

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 15 files changed, 92 insertions(+), 50 deletions(-))
Terraform Beta: Diff ( 17 files changed, 111 insertions(+), 58 deletions(-))

[danawillow]

LGTM assuming tests for changed resources are passing

[emilymye]

https://ci-oss.hashicorp.engineering/viewLog.html?buildId=97979&buildTypeId=GoogleCloudBeta_ProviderGoogleCloudBetaMmUpstream