feat(rm): Add MXFP dtype combinations to OpCast
- Implements the new dtype combinations in OpCast
- Refactors some code to simplify CastHelper. It seems like there is much more simplification that could be done.
- Adds support for FP8/6/4 outputs in ModelRunner
- The getHalfUlp utility for unit tests was moved to test_utils.h
- Now getHalfUlp utility correctly computes ULPs for subnormal values
Signed-off-by: Ian Tayler Lessa ian.taylerlessa@arm.com