Add support for AlloyDB Cluster Major Version Upgrade

[GauravJain21]

Add support for AlloyDB Cluster Major Version Upgrade

This PR adds support for allowing users to upgrade their AlloyDB cluster's PG major version by just updating the database_version field inside the cluster.

Release Note Template for Downstream PRs (will be copied)

alloydb: added support for upgrading `database_version` in `google_alloydb_cluster` resource

[github-actions]

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@NickElliot, a repository maintainer, has been assigned to review your changes. If you have not received review feedback within 2 business days, please leave a comment on this PR asking them to take a look.

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[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 ( 3 files changed, 132 insertions(+), 11 deletions(-))
google-beta provider: Diff ( 3 files changed, 132 insertions(+), 11 deletions(-))

[modular-magician]

Tests analytics

Total tests: 75
Passed tests: 71
Skipped tests: 2
Affected tests: 2

Click here to see the affected service packages

• alloydb

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

• TestAccAlloydbCluster_update
• TestAccAlloydbCluster_upgrade

Get to know how VCR tests work

[modular-magician]

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

🟢 No issues found for passed tests after REPLAYING rerun.

---

🔴 Tests failed during RECORDING mode:
TestAccAlloydbCluster_upgrade [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