App check debug token

[modular-magician]

Add support for App Check debug tokens. Part of hashicorp/terraform-provider-google#17095

Note to reviewers: I used a trick to populate a derived field debug_token_id in name's flattening phase. I've tried other hooks such as custom decoders, post_create, etc, but they are injected in awkward places i.e. after the reference of debug_token_id to populate the id, which leads to more overriding code. This one minimizes the amount of custom code and sits just right. I'm open to suggestions if there are better ways. I see an existing similar usage in https://github.com/GoogleCloudPlatform/magic-modules/blob/9c04e74ab0fa1d7198a7a6d15c87143960ac814d/mmv1/templates/terraform/custom_flatten/bigtable_app_profile_routing.erb#L25

Release Note Template for Downstream PRs (will be copied)

`google_firebase_app_check_debug_token`

Derived from GoogleCloudPlatform/magic-modules#9930

[conventional-commit-lint-gcf]

🤖 I detect that the PR title and the commit message differ and there's only one commit. To use the PR title for the commit history, you can use Github's automerge feature with squashing, or use automerge label. Good luck human!

-- conventional-commit-lint bot
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