Add functionality for proper alignment when a fixed delay is specified

This CL adds functionality for adjusting the reported stream delay
based on any specified fixed delay, such that the resulting delay
can be used for proper pre-alignment before the delay estimator
has been able to properly activate..

Bug: chromium:415954529
Change-Id: I2a752c5f480a7d01404ed258dcb0ca83c3ca7a60
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/411841
Reviewed-by: Jesus de Vicente Pena <devicentepena@webrtc.org>
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#45742}