[Tab Switcher] update color dot icon geometry

1) 24dp with avatar 16dp + inner stroke 2x2dp + outer stroke 2x2dp
   radius = 12dp
2) 22dp without avatar 18dp + 2x2dp stroke
   radius = 11 dp
3) Add 2dp margin to the start of avatars to fix centering.
4) Change padding from 11dp all around to center_vertical with 11dp
   start and 9dp end.
5) Remove stroke updates as stroke is now constant 2dp.

There is still some strange end padding/margin inside
SharedImageTilesCoordinator's provided view. However, it doesn't impact
the rendered outcome anymore. It would be nice if the bounds of the
container matched the content though. Something to be looked into in
a follow-up probably.

Screenshots:
https://drive.google.com/drive/folders/1-NJmY1l15uiQS_iR78_LNabYv3HeiPbD?usp=sharing


Low-Coverage-Reason: COVERAGE_UNDERREPORTED there are tests for this in TabGroupColorViewProviderUnitTest. I'm not sure why this isn't being counted.
Bug: 376907446
Change-Id: I5e30f80bdd4d4b599053ced0e671959735f0847d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6006776
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Reviewed-by: Hailey Wang <haileywang@google.com>
Commit-Queue: Calder Kitagawa <ckitagawa@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1381982}