[Android] Make equal both Features processors in //chrome and //base
Move the CachedFlags and FieldTrials override and resetting logic to FeaturesBase such that chrome/.../Features.java and util/.../Features.java are equivalent.
They are not mutually interchangeable so the simplest migration is to move usages of the //chrome one to the //base one, then delete the //chrome Features.java.
Make //chrome's Features.JUnitProcessor and Features.InstrumentationProcessor compatible with both //chrome and //base Features.EnableFeatures and Features.DisableFeatures.
This forward compatibility allows changing the annotations before the processor, which is necessary for downstream tests that rely on InstrumentationProcessor being a default rule in ChromeJUnit4ClassRunner.
The //chrome version is being moved to //base. Migrate usages to reference the //base Features.JUnitProcessor and .InstrumentationProcessor, along with @EnableFeatures and @DisableFeatures.
Mark the //chrome Features as deprecated, soon to be removed.