fix: ImportResolver handles nested types.

Even though we don't support nested type declarations, unstuctured
parcelables can be nested types.

Now ImportResolver searches upwards [./p/Outer/Inner.aidl,
./p/Outer.aidl, ./p.aidl] for "p.Outer.Inner".

See the added unit test.

This is a small step forward to support nested type decls.

Bug: 182508839
Test: aidl_unittests
Change-Id: Ifd96c131c08b0067475d9bf25c72e3f825a2a9a9
3 files changed