Implement pacing interceptor

[mengelbart]

Description

Implements a pacing interceptor separate from congestion control. The interceptor calls back to implementations of the Pacer interface whenever a packet is sent.

[codecov]

Codecov Report

❌ Patch coverage is 74.33628% with 29 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.45%. Comparing base (40d68d9) to head (4d47254).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/pacing/interceptor.go	81.55%	14 Missing and 5 partials ⚠️
pkg/pacing/rate_limit_pacer.go	0.00%	10 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #309      +/-   ##
==========================================
- Coverage   79.69%   79.45%   -0.25%     
==========================================
  Files          82       84       +2     
  Lines        4063     4176     +113     
==========================================
+ Hits         3238     3318      +80     
- Misses        659      685      +26     
- Partials      166      173       +7     

Flag	Coverage Δ
go	79.45% <74.33%> (-0.25%)	⬇️

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[JoTurk]

We don't seem to be calling ticker.Stop()

[mengelbart]

I added a defer ticker.Stop(), although I don't think we necessarily need it since Go 1.23, because the ticker should be garbage collected when it is unreferenced, even without calling Stop. At least that's how I understand the documentation.

[JoTurk]

I read about this, sadly. it's going to be a while before we can drop go 1.22 and 1.21 in pion, also the new behavior is eligible for collection immediately, and it doesn't say that it’s collected immediately, at least from my understanding, but i didn't test it.
Thanks.