Add BinderResult and expected<> gtest matchers

Add BinderResult which is short-hand for a Result with error-type
binder::Status, which is preferred type for implementing binder
interfaces.

Add gmock matchers which unwrap expected types in either the expected or
error directions for ease of testing.

Test: atest NativePermissionControllerTest with subsequent CL
Flag: EXEMPT: adding code without use
Bug: 338089555
Change-Id: I00f4f71e7d10cadfe6a0b2a628b887df9931e447