[ios] Compiles ChromeEarlGreyUI under EG2.

Refactors code in ChromeEarlGreyUI that has a dependency on app code.
This includes:
- Matchers that require NSString accessibility ID constants.
- A helper that looked at the keyWindow's size class.
- A matcher for the scroll view of the current WebState.
- Helpers that called grey_kindOfClass() with a Class that is only
  available in the app process.

These helpers and matchers are converted to their EG2 equivalents.


Change-Id: I4f6dfb82ecf8d0fd5f10cb8add225383b3f0d9d8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1619840
Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Rohit Rao <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661410}
10 files changed