Build:

Inlcudes Some general build hygeine and simplification
Creates an aconfig flag declaration and java library
Add java_defaults rules for library and app for common settings

Tests:

Added direct dep on JUnit (was indirectly pulled in)
Remove source dependency (on main code) from the test app target
Remove optimization and dexopt from the debug app target

Test: All existing tests pass;
	atest IntentResolverUnitTests
Test: Setup using ASfP (Android studio for platform)
Bug: 296633726
Change-Id: I8046f76aa20957342ddddabc8861c0a8fe25e0fb