Update Typeface.Builder API to reflect API feedback.

- Stop pooling and remove reset method.
- Introduce overloaded constructors instead of setSource methods.
- Make italic parameter boolean and treat "not called" as
  RESOLVE_BY_FONT_TABLE.
- Remove constants and move them to Typeface with private static
  constant.
- Fix JavaDoc.

Bug: 37082657
Test: android.graphics.cts.TypefaceTest passed
Change-Id: I0c50cf3e2d50c0021f7e12bbb7ed7ae89fa1c2a1