testing/buildbot: enable bot existence checking for fyi, android.fyi, lkgr waterfalls

Looks like these waterfalls now exist in luci-milo.cfg, so this is now possible.

- Remove no-longer-existing bots "Chromium Mac 10.11",
  "Chromium Mac 10.11 Force Mac Toolchain", "Chromium Win 10 GCE Tests"

- "Chromium Win 10 GCE Tests" was the only bot using chromium_win_fyi_gtests,
  so remove that too (since the bot didn't exist, it wasn't used previously
  either), which in return was the only user of chrome_cleaner_gtests, so
  remove that too.

- Fix case sensitivity misspellings: We're not consistent about if bots are
  called ASan (more common) or ASAN (less common, but present).

- While here, also remove some remaining references to PGO from mb_config.pyl.

Follow-up to https://chromium-review.googlesource.com/c/chromium/src/+/1061597

Bug: 843511,820422
Change-Id: I70518fdedfab23c807afdcd8bb335a9aeacf09dc
Reviewed-on: https://chromium-review.googlesource.com/1093159
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565711}
8 files changed