Introducing CSQL replica promotion support in terraform

[modular-magician]

This change is regarding following feature ask #10486
Introducing replica promotion support on terraform provider. This change will allow users to promote read replica as stand alone primary instance. To promote read replica as primary instance following steps are required:

• User sets instance_type property as CLOUD_SQL_INSTANCE
• User removes master_instance_name and replica_configuration properties from replica terraform script.
• User runs terraform apply

Appropriate terraform provider level validation are introduced:

• In case of promote replica request, replica instance can not have master_instance_name and replica_configuration set.
• This validation will be performed at the time of terraform plan and terraform apply

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)

sql: added replica promotion support to `google_sql_database_instance`. This change will allow users to promote read replica as stand alone primary instance.

Derived from GoogleCloudPlatform/magic-modules#7190