Add support for int-to-byte in the optimizing compiler.

- Add support for the int-to-byte Dex instruction in the
  optimizing compiler.
- Implement the ARM and Thumb-2 SBFX instructions.
- Generate x86, x86-64 and ARM (but not ARM64) code for
  char to byte, short to byte and int to byte
  HTypeConversion nodes.
- Add related tests to test/422-type-conversion.

Change-Id: Ic8b8911b90d4b5281fad15bcee96bc3ee85dc577