Clamp stable target bitrate to min/max allocated bitrate.
Clamp stable target bitrate to min/max allocated bitrate.

Currently, the stable target can grow to 2x the max allocated bitrate.

Bug: None
Change-Id: I71657cb49ebebd429aae0bcd2e2978938252115c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/170222
Reviewed-by: Sam Zackrisson <b1a93beadfe1d2f7f0106ee02b6ffcdc950aa103@webrtc.org>
Reviewed-by: Sebastian Jansson <c24d1bc144eb7c11e553f59153fa17dba85ca83e@webrtc.org>
Commit-Queue: Jakob Ivarsson <9ca81c2aa4aa86256fc426d7d57eed586c9fd3ac@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#30776}

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