Replace Buffer::CreateUninitializedWithSize

This dangerous method can be replaced in almost all cases with
Buffer::CreateWithCapacity() and AppendData(maxsize, lambda),
which sets size in a safe manner (as long as the lambda does
what it claims to do).

Bug: webrtc:42223681
Change-Id: If6d8af914e5958cdafddc6008b1336d2216168b7
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/442000
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#46658}