fix(instrumentation-pg): not add duplicate listeners to pg pool

[maryliag]

Which problem is this PR solving?

• Addresses Memory leak in instrumentation-pg #2479

Short description of the changes

• Checks if listeners for pg pool events were already added before trying to add them.
• Generate poolName only once, and use the same on all updates, instead of calculating every time

[codecov]

Codecov Report

Attention: Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.

Project coverage is 90.75%. Comparing base (b043ffb) to head (64a407f).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...elemetry-instrumentation-pg/src/instrumentation.ts	92.30%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2484   +/-   ##
=======================================
  Coverage   90.74%   90.75%           
=======================================
  Files         156      157    +1     
  Lines        7728     7734    +6     
  Branches     1590     1591    +1     
=======================================
+ Hits         7013     7019    +6     
  Misses        715      715           

Files with missing lines	Coverage Δ
...telemetry-instrumentation-pg/src/internal-types.ts	100.00% <100.00%> (ø)
...node/opentelemetry-instrumentation-pg/src/utils.ts	97.61% <ø> (-0.02%)	⬇️
...elemetry-instrumentation-pg/src/instrumentation.ts	90.16% <92.30%> (+0.33%)	⬆️

[pichlermarc]

thanks for taking care of this. 👍
One comment about the added property - otherwise this looks good to be merged.

[pichlermarc]

Thanks for working on this. There's one more comment I have about he semconv stability flag, once addressed we can merge this.

[pichlermarc]

thank you for taking care of this 👍