Cap feedback interval to max_time_between_feedback if send BWE is zero

When send bandwidth estimate is zero and feedback is bandwidth limited,
set the next possible feedback send time to last_feedback_sent_time +
max_time_between_feedback. This avoids dividing by zero in debt pacing
while still respecting the maximum time between feedbacks.

Bug: webrtc:519655843
Change-Id: Id28188dd6e480636cbf15cea5ca150263791b8bc
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/506360
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Per Kjellander <perkj@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#48759}