Refactor M68K instruction printing and enhance bitfield support

- Improved the M68K instruction printer by refactoring the handling of register bits and addressing modes.
- Introduced new functions for printing scale factors, index registers, and immediate values.
- Enhanced bitfield handling in the `m68k_op_mem` structure to support both static and register-encoded values.
- Updated tests to reflect changes in instruction formatting, particularly for `cinvl`, `cpushl`, and `cas2` instructions.
- Added new test cases for bitfield instructions to ensure correct parsing and output.
- Add details to tests/m68k.yaml

Author: b1llow