[base] Move SkMSAN into base

With some other misc fixes, like improving the IWYU mapping file.

Change-Id: I09a497825e9adc5d13a87914afe641691b42da40
Bug: skia:13983
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/642397
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
15 files changed