fix: prevent duplicated UpdateFunction calls

[IzaakGough]

Fixes #10731

Summary

Prevent Cloud Functions update requests from enabling the premature-close retry path, which could cause duplicate UpdateFunction calls.

Problem/Root Cause

PATCH update requests were eligible for the keep-alive retry path when a premature-close error occurred. For Cloud Functions updates, that could reissue the operation and produce duplicate update calls.

Solution/Changes

Add a per-request retryOnPrematureClose flag to the API client and disable it for Cloud Functions v1 and v2 update calls. Update the request tests to cover both the disabled and default retry behavior.

Testing

• Added unit coverage for the premature-close retry path in src/apiv2.spec.ts.

[gemini-code-assist]

Code Review

This pull request restricts retrying requests on premature close errors to specific HTTP methods by introducing a helper function, and adds corresponding unit tests. The review feedback correctly notes that the helper function is named isIdempotentMethod but includes POST, which is non-idempotent. It suggests renaming the function to shouldRetryMethod to maintain semantic correctness.