GitLab

Steps:
- Introduced the xcode cache x11e146 in //infra/config/lib/builders.star
- The default xcode cache is set in //lib/ci.star under fyi_ios_builder
  definition, but we only want to roll ios13-sdk-simulator. Check that
  cache param is overridable, and override it with the newly introduced
  xcode_cache.x11e146. Update the properties so that the builder
  uses this too.
- 11e146 needs Mac OS 10.15. This definition did not support overriding
  the default OS, so OS param was introduced into fyi_ios_builder.
  Set OS for the builder to os.MAC_10_15.
- Trybot for ios13-sdk-sim is under //infra/config/buckets/try.star.
  - the definition is under //infra/lib/try.star, and didn't support
    overriding the default variables, so they've been included into
    the parameters.
  - //infra/config/buckets/try.star was missing the xcode_cache import,
    so this was appended.
  - same w/ the ci definition, adding the property too.
- Creating variants with 13.4 and updating all sim version usage for
    this bot from 13.3 to 13.4. 12.4 should be fat bundled.
- Updating xcode and xcode cache version for this bot by creating
  xcode_11e146 in mixins.pyl and apply that in waterfalls.pyl.

Bug: 1065456
Change-Id: I54e720efddc05a55ab69f485b9ceb55c1deafa59
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2134940
Commit-Queue: Jeff Yoon <jeffyoon@chromium.org>
Reviewed-by: Garrett Beaty <gbeaty@chromium.org>
Cr-Commit-Position: refs/heads/master@{#758973}