Find and load ANGLE rules, pass to libEGL

In order to load a text file from an APK, it must be present
in the assets folder and be uncompressed. The AssetManager can
find assets from any application, so we point it at ANGLE. We
then pass the file descriptor, offset, and size, down to the loader
so it can parse json from the asset.

Bug: 80239516
Test: Manual build, ensure we can inspect rules from modified APK
Test: cts-tradefed run singleCommand cts -m CtsAngleIntegrationHostTestCases
Change-Id: Ib3ecce34b043753b2894915975b6dd8440154ae2
(cherry-picked from commit cfaa0ba52fcf60578acdd64bc4dc9a00f6e300ed)