Deprecate cricket::MediaType and associated aliases

Also update remaining uses of cricket::MediaType to be webrtc::MediaType
Removing superfluous prefixes will be done in a later stage as part
of cleanup after the namespace merge.

Bug: webrtc:42222911
Change-Id: If5101e2aefe12b6a772ae6af308ee0dca666daba
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/382660
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Auto-Submit: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#44237}