Adding unbundled uiautomator jar from AOSP to third_party.

The unbundled uiautomator jar will allow us to run Android
uiautomator tests via Android instrumentation. This will
simplify our test runner code as we can remove uiautomator
specific test runner code.

Additionally, the instrumentation-based uiautomator is more
up-to-date than the shell-based uiautomator embedded inside the
Android platform that we are currently using.

BUG=488573

Review URL: https://codereview.chromium.org/1157563011

Cr-Commit-Position: refs/heads/master@{#334428}

• .gitignore[diff]
• DEPS[diff]
• third_party/ub-uiautomator/BUILD.gn[Added - diff]
• third_party/ub-uiautomator/LICENSE[Added - diff]
• third_party/ub-uiautomator/OWNERS[Added - diff]
• third_party/ub-uiautomator/README.chromium[Added - diff]
• third_party/ub-uiautomator/ub-uiautomator.gyp[Added - diff]