This adds runtime/docs/aot_binary_size_analysis.md describing how to
visualize the breakdown of generated code size from our AOT.
Change-Id: I63ae3728db808532fad0ca178e1947e5b8280521
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/112397
Reviewed-by: Michael Thomsen <mit@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>