feat(apigee_registry)!: replace apigee registry gems with tombstones

[torreypayne]

Replaces google-cloud-apigee_registry (wrapper gem) and google-cloud-apigee_registry-v1 (versioned client gem) with minimal tombstone packages.

Details of Changes

• Generated via toys tombstone-library using updated templates from googleapis/ruby-common-tools#453.
• Bumps google-cloud-apigee_registry to 2.0.0 (SemVer Major) and google-cloud-apigee_registry-v1 to 1.0.0 (SemVer Major).
• Includes minimal Rakefile with require "bundler/gem_tasks" to ensure automated release builds (rake build) succeed out of the box during CI/CD packaging.
• Removes all runtime dependencies and functional code, leaving only version constants, README, LICENSE, and .yardopts.

BEGIN_COMMIT_OVERRIDE
feat(google-cloud-apigee_registry)!: replace gem with tombstone
Release-As: 2.0.0
feat(google-cloud-apigee_registry-v1)!: replace gem with tombstone
Release-As: 1.0.0
END_COMMIT_OVERRIDE

[aandreassa]

@torreypayne I get what you are trying to do, but BEGIN_COMMIT_OVERRIDE block won't work since it has two Release-As entries. I recommend just removing it and using after the fact if you still need it.

Merging as feat! should be enough to bump them individually! (to their next major versions, 2.0.0 and 1.0.0)

[aandreassa]

Please fix