Remove JavaScriptEngine client library from Chromium

The client library is owned by AndroidX and we will follow the AndroidX policies for development, testing and release.

Bug: 1393357
Test: autoninja -C out/Default javascriptengine_test && out/Default/bin/run_javascriptengine_test
Change-Id: I523399091116a10540bae6648459b092f07f47ca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4055867


Reviewed-by: Richard Coles <torne@chromium.org>
Commit-Queue: Abhijith Nair <abhijithnair@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1086244}