ScreamV2, add application limited state

To enter application limited state:
bool alr = max_allowed_ref_window() < ref_window_

In application limited state, smoothed RTT use a slower EWMA filter in order to reduce RTT variations.
It make RTT decrease slower due to that link capacity is not utilized. It make RTT increase slower in order to not decrease target rate due
to RTT spikes.
RTT is still updated though to ensure that RTT eventually will decrease to avoid getting stuck at a low target rate if RTT was high due to
a delay spike when entering application limited state.

ref_window_ will not increase in application limited state.

Bug: webrtc:447037083
Change-Id: I2c5767bfeefc822031ffaf9eaf74b19759cc511b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/469940
Reviewed-by: Björn Terelius <terelius@webrtc.org>
Commit-Queue: Per Kjellander <perkj@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#47639}