Add metadataFilters to GlobalForwardingRule

[tysen]

To support Traffic Director.

Release Note for Downstream PRs (will be copied)

`google_compute_global_forwarding_rule` now supports `metadata_filters`.

[modular-magician]

Hi! I'm the modular magician, I work on Magic Modules.
I see that this PR has already had some downstream PRs generated. Any open downstreams are already updated to your most recent commit, cad1aed.

Pull request statuses

New Pull Requests

I built this PR into one or more new PRs on other repositories, and when those are closed, this PR will also be merged and closed.
depends: hashicorp/terraform-provider-google-beta#1160
depends: GoogleCloudPlatform/terraform-google-conversion#208
depends: hashicorp/terraform-provider-google#4495
depends: ansible-collections/google.cloud#8
depends: modular-magician/inspec-gcp#208

[modular-magician]

Hi! I'm the modular magician, I work on Magic Modules.
I see that this PR has already had some downstream PRs generated. Any open downstreams are already updated to your most recent commit, a835caa.

Pull request statuses

terraform-provider-google-beta already has an open PR.
terraform-google-conversion already has an open PR.
terraform-provider-google already has an open PR.
Ansible already has an open PR.
InSpec already has an open PR.

New Pull Requests

I didn't open any new pull requests because of this PR.