Make refactored BWE compatible with the old API

[mengelbart]

Description

This makes the refactored BWE implementation compatible with the existing cc.Interceptor by implementing the cc.BandwidthEstimator interface and wrapping the new ccfb.Interceptor in the old cc.Interceptor. It does not (yet) implement pacing because that would cause nested pacing with the old implementation. Instead of merging this PR, I would actually prefer to remove the old API completely (by removing the gcc and cc packages).

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 60.70560% with 323 lines in your changes missing coverage. Please review.

Project coverage is 69.79%. Comparing base (c06f448) to head (9c58291).

Files with missing lines	Patch %	Lines
pkg/bwe/deprecated_bwe_api.go	0.00%	73 Missing :warning:
pkg/bwe/kalman.go	0.00%	66 Missing :warning:
pkg/bwe/delay_rate_controller.go	0.00%	57 Missing :warning:
pkg/bwe/send_side_bwe.go	0.00%	28 Missing :warning:
pkg/ccfb/interceptor.go	78.29%	22 Missing and 6 partials :warning:
pkg/ccfb/twcc_receiver.go	70.83%	21 Missing :warning:
pkg/bwe/state.go	70.27%	11 Missing :warning:
pkg/cc/interceptor.go	0.00%	11 Missing :warning:
pkg/bwe/usage.go	0.00%	10 Missing :warning:
pkg/bwe/rate_controller.go	83.33%	8 Missing :warning:
... and 4 more

:x: Your patch check has failed because the patch coverage (60.70%) is below the target coverage (70.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #308      +/-   ##
==========================================
- Coverage   71.38%   69.79%   -1.60%     
==========================================
  Files          79       98      +19     
  Lines        4526     5340     +814     
==========================================
+ Hits         3231     3727     +496     
- Misses       1158     1469     +311     
- Partials      137      144       +7     

Flag	Coverage Δ
go	69.79% <60.70%> (-1.47%)	:arrow_down:
wasm	?

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[JoTurk]

Again I'm sorry about the conflicts, we had to ship the lint upgrades, Let me know, And I'll fix them for this branch :)