Pacer: Reduce TQ wake up and improve packet size estimation

The TQ Pacer schedules delayed task according to target time of
PacingController. It drains all valid ProcessPackets() in single loop,
denies retired scheduled tasks, and round up the timeout to 1ms.

This CL also improves packet size estimation in TQ Pacer by removing
zero initialization, and introduces `include_overhead_` configuration.

Tests:
1. webrtc_perf_tests: MaybeProcessPackets() calls
  2075147 -> 2007995

2. module_unittests: MaybeProcessPackets() calls
  203393 -> 183563

3. peerconnection_unittests: MaybeProcessPackets() calls
  66713-> 64333

Bug: webrtc:13417, webrtc:13437
Change-Id: I18eb0a36dbe063c606b1f27014df74a65ebfc486
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/242962
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Commit-Queue: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36179}