Combine calendar picker CSS files

This CL combines these two CSS files into one:
  renderer/core/html/forms/resources/calendar_picker_refresh.css
  renderer/core/html/forms/resources/calendarPicker.css

This looks like a lot of changes, but it is just the insertion of
the contents of calendar_picker_refresh.css into the existing
selectors within calendarPicker.css. The test coverage for the
calendar pickers is fairly good, so I'm relatively sure this does
not change behavior.

Bug: 1208983
Change-Id: Idfbd51348f241557f4312a41ae4b97b3be0dec12
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2897957


Auto-Submit: Mason Freed <masonf@chromium.org>
Commit-Queue: Philip Rogers <pdr@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Reviewed-by: Joey Arhar <jarhar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#887358}