Fix upsert on gcp starter indexes

[izellevy]

Problem

Gcp starter does not support delete by metadata that fails the upsert.

Solution

Update the is_serverless_env function to catch on gcp-starter.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Infrastructure change (CI configs, etc)
• Non-code change (docs, etc)
• None of the above: (explain here)

Test Plan

Improved parameterization in testing.

[miararoy]

lgtm!