WIP: support for pgwire SNI to skip Frontegg API call

[pH14]

Still a draft, but I got curious how the balancers work and nerdsniped myself into hooking up pgwire sni support. It seems to work locally, but there are a lot of tricky edge cases that I only know how to test on a personal stack that I haven't gotten around to.

Motivation

Fixes #23907

Tips for reviewer

Checklist

• This PR has adequate test coverage / QA involvement has been duly considered. (trigger-ci for additional test/nightly runs)
• This PR has an associated up-to-date design doc, is a design doc (template), or is sufficiently small to not require a design.
• If this PR evolves an existing $T ⇔ Proto$T mapping (possibly in a backwards-incompatible way), then it is tagged with a T-proto label.
• If this PR will require changes to cloud orchestration or tests, there is a companion cloud PR to account for those changes that is tagged with the release-blocker label (example).
• This PR includes the following user-facing behavior changes: