Update HashiCorp copyright headers

[bbasata]

Notes for reviewers:

• This PR may be best reviewed commit-by-commit. Each commit is a unit of updating.
• This PR may be best merged on the day after a release (or release branch point), as a buffer for any downstream repo effects.

This PR updates copyright headers in the downstream generated provider repos in the hashicorp GitHub organization. This is consistent with all other HashiCorp official Terraform provider repositories.

This change supersedes copyright header PRs in the downstream repos, such as hashicorp/terraform-provider-google#25439.

I have drawn upon prior art and research by @SarahFrench, including:

• Allow adding copyright headers to non-templated files in downstream-selective way #7937
• Add copyright header on handwritten files copied by tpgtools #8073
• Add copyright headers to files in .teamcity/ #8373
• Add copyright header to file generated by tools/teamcity-generator #8501

TODO:

• tools/go-changelog

Release Note Template for Downstream PRs (will be copied)

See Write release notes for guidance.

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

google provider: Diff ( 3884 files changed, 3946 insertions(+), 4097 deletions(-))
google-beta provider: Diff ( 4102 files changed, 4164 insertions(+), 4315 deletions(-))

[modular-magician]

Tests analytics

Total tests: 6093
Passed tests: 5455
Skipped tests: 636
Affected tests: 2

Click here to see the affected service packages

All service packages are affected

Action taken

Found 2 affected test(s) by replaying old test recordings. Starting RECORDING based on the most recent commit. Click here to see the affected tests

• TestAccGKEHubFeatureMembership_gkehubFeatureAcmUpdate
• TestAccGKEHubFeatureMembership_gkehubFeaturePolicyController

Get to know how VCR tests work

[modular-magician]

🟢 Tests passed during RECORDING mode:
TestAccGKEHubFeatureMembership_gkehubFeatureAcmUpdate [Debug log]

🟢 No issues found for passed tests after REPLAYING rerun.

---

🔴 Tests failed during RECORDING mode:
TestAccGKEHubFeatureMembership_gkehubFeaturePolicyController [Error message] [Debug log]

🔴 Errors occurred during RECORDING mode. Please fix them to complete your PR.

View the build log or the debug log for each test