feat: support wrapper types for autopagination

[shollyman]

This PR widens support for autopagination in the go gapic generator. Changes:

• enable autopaging detection to include wrapper types in the heuristic
• allowlist control for enabling wrapper support based on proto package name
• templating changes for support
• augment the autopagination denylist to avoid generating a paginatinated signature for an additional API/method

Things still outstanding:

• Testing depth: this validates detection, but doesn't expand goldens testing to use a wrapper-based list RPC. That said, we only expect the single service to leverage this, and I have verified the generated client out of band.

[shollyman]

looks like the showcase testing in integration testing is broken in general, not due to this PR: #1552

[quartzmo]

This latest revision improves this PR a lot! I'm impressed with how much easier it is to understand. Approving, with nit for one docs typo.