Verify regex on CharSequenceTransformation

... Also
- change the constructor of the Builder of this class
- Do not crash if the subsitutions for the regexes are invalid

Change-Id: I965d5830f4932eb40ec22d7fa308815955920a99
Bug: 62534917
Test: cts-tradefed run cts-dev -m CtsAutoFillServiceTestCases
6 files changed