feat(sl): Add MxFP datatypes and new operators

• Added new datatypes:

  • FP6E2M3
  • FP6E3M2
  • FP4E2M1
  • FP8UE8M0

• Added 3 operators with attributes:

  • MatMulTBlockScaled (block_size)
  • CastFromBlockScaled (block_size)
  • CastToBlockScaled (block_size, stochastic_round)

These changes extend the schema to support MxFP datatypes and block-scaled operations.

Signed-off-by: Yuvaraj Venkatesh yuvaraj.venkatesh@arm.com