Revert "Refactor and remove media_optimization::MediaOptimization."

This reverts commit 07276e4f89a93b1479d7aeefa53b4fc32daf001b.

Reason for revert: Speculative revert due to downstream crashes.

Original change's description:
> Refactor and remove media_optimization::MediaOptimization.
> 
> This CL removes MediaOptmization and folds some of its functionality
> into VideoStreamEncoder.
> 
> The FPS tracking is now handled by a RateStatistics instance. Frame
> dropping is still handled by FrameDropper. Both of these now live
> directly in VideoStreamEncoder.
> There is no intended change in behavior from this CL, but due to a new
> way of measuring frame rate, some minor perf changes can be expected.
> 
> A small change in behavior is that OnBitrateUpdated is now called
> directly rather than on the next frame. Since both encoding frame and
> setting rate allocations happen on the encoder worker thread, there's
> really no reason to cache bitrates and wait until the next frame.
> An edge case though is that if a new bitrate is set before the first
> frame, we must remember that bitrate and then apply it after the video
> bitrate allocator has been first created.
> 
> In addition to existing unit tests, manual tests have been used to
> confirm that frame dropping works as expected with misbehaving encoders.
> 
> Bug: webrtc:10164
> Change-Id: I7ee9c8d3c4f2bcf23c8c420310b05a4d35d94744
> Reviewed-on: https://webrtc-review.googlesource.com/c/115620
> Commit-Queue: Erik Språng <sprang@webrtc.org>
> Reviewed-by: Niels Moller <nisse@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#26147}

TBR=nisse@webrtc.org,sprang@webrtc.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: webrtc:10164
Change-Id: Ie0dae19dd012bc09e793c9661a45823fd760c20c
Reviewed-on: https://webrtc-review.googlesource.com/c/116780
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26191}

modules/video_coding/BUILD.gn

@@ -133,6 +133,8 @@ rtc_static_library("video_coding") {
     "jitter_estimator.h",
     "media_opt_util.cc",
     "media_opt_util.h",
+    "media_optimization.cc",
+    "media_optimization.h",
     "nack_fec_tables.h",
     "packet_buffer.cc",
     "packet_buffer.h",