Moar changes for Autofill Field Classification mechanism:

- Changed max score to float (range 0.0 - 1.0).
- Replaced getTopMatch() to getMatches().
- Created a Scorer interface with a default edit-distance implementation.
- Added a isFieldClassificationEnabled() method.

Test: atest CtsAutoFillServiceTestCases:FieldsClassificationTest
Test: atest CtsAutoFillServiceTestCases:EditDistanceScorerTest
Test: atest CtsAutoFillServiceTestCases:UserDataTest
Test: atest FrameworksCoreTests:SettingsBackupTest

Bug: 68045531

Change-Id: Ice6cbf548053b86b47980d9664a3a21219c0ff08