Add Certificate Authority Resource (Certificate Authority Service)

[modular-magician]

#7657

Adds "google_privateca_certificate_authority" (name is duplicated because "Certificate Authority" is also the product name)

See https://cloud.google.com/certificate-authority-service/docs/reference/rest/v1beta1/projects.locations.certificateAuthorities for resource documentation.

Notes:

• This change doesn't implement support for subordinate CAs, which require additional customization because they must be activated.

Customizations:

• Use POST :scheduleDelete to delete the resource (delete is not supported)
• On pre_delete, POST :disable to disable the resources (required for scheduling deletion)
• Check resource deletion by checking that status is DELETION_PENDING

If this PR is for Terraform, I acknowledge that I have:

• Searched through the issue tracker for an open issue that this either resolves or contributes to, commented on it to claim it, and written "fixes {url}" or "part of {url}" in this PR description. If there were no relevant open issues, I opened one and commented that I would like to work on it (not necessary for very small changes).
• Generated Terraform, and ran make test and make lint to ensure it passes unit and linter tests.
• Ensured that all new fields I added that can be set by a user appear in at least one example (for generated resources) or third_party test (for handwritten resources or update tests).
• Ran relevant acceptance tests (If the acceptance tests do not yet pass or you are unable to run them, please let your reviewer know).
• Read the Release Notes Guide before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

`google_privateca_certificate_authority`

Derived from GoogleCloudPlatform/magic-modules#4382

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