feat(pg): add pg-pool.release span

[MUSKANNISHAD]

Fixes #1976

This PR adds a pg-pool.release span by instrumenting client.release() on the
client returned from pool.connect().

This allows tracing the full PostgreSQL pool lifecycle
(connect → query → release) while keeping existing pool metrics behavior unchanged.

[MUSKANNISHAD]

I’ve added tracing for pg-pool.release by wrapping client.release() on the client returned from pool.connect(). This captures the full pool lifecycle while keeping metrics unchanged. I’ve opened a PR for review.

[maryliag]

please add tests to validate your changes

[MUSKANNISHAD]

please add tests to validate your changes
Thanks for the review!
I’ve added tests covering the new pg-pool.release span and updated the existing test suite accordingly.
The changes are included in the latest commit — please let me know if you’d like additional coverage or adjustments.