Pool checkout tweak

[levkk]

Description

• Attempt to fetch another connection from the pool if a health check fails while checking out a connection
• Remove double-removal of water from connection pool, move checkout timeout logic up to pool from waiter

[codecov]

Codecov Report

❌ Patch coverage is 94.52055% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
pgdog/src/backend/pool/pool_impl.rs	95.23%	2 Missing ⚠️
pgdog/src/backend/pool/healthcheck.rs	66.66%	1 Missing ⚠️
pgdog/src/backend/pool/waiting.rs	88.88%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!