[AW] Log WebView crash info in WebView's crash dir

- Log WebView crashs' info keys ("app-package-name" and "variations") as
  well as crash-local-id and capture-time to log files under WebView's
  crash dir. Each crash has its unique log file with a JSON object that
  contains crash info.

- Move CrashInfoLoader.java to a separate build target to be shared
  between the UI and crash service code.

Bug: 958340

Change-Id: I446204cc400bc05e6bac4cf40001469ed0ccc7fe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1593375
Commit-Queue: Hazem Ashmawy <hazems@chromium.org>
Reviewed-by: Tobias Sargeant <tobiasjs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#679573}