Hide packing structure from public API

The hyphen edit is packed into 8bit integer in native library, but this
should not be exposed to public API as API council suggested.

This CL includes:
- Removing packing structure from HyphenEdit and move constants from
  Hyphenator to Paint.
- Replace LineBreaker's getLineHyphenEdit with two separate start/end
  function.
- Replace Paint's getHyphenEdit with two separate start/end function.
- StaticLayout still relies on this packing mechanism but no longer need
  to be the same packing structure as in Minikin.

Bug: 124794844
Test: atest CtsGraphicsTestCases
Test: atest CtsTextTestCases
Change-Id: I8206061f554cf6e119b2b565162f54317eac630a