GpuService: Add FeatureOverrideParser

Add the class FeatureOverrideParser to GpuService. This class parses
feature_config protobufs and converts the values to FeatureOverrides,
which is used by GraphicsEnv.

Feature overrides are used to toggle ANGLE driver features.

Bug: 372694741
Test: atest gpuservice_unittest
Flag: com.android.graphics.graphicsenv.flags.feature_overrides
Change-Id: I5c27d1f2e9d370b33a1ec350e36833bcb330e8fd