[GlobalISel] Add Floating Point Type to LLT

[tgymnich]

This issue tracks progress on the implementation of an additional LLT kind for floating point types as proposed in this RFC: [RFC][GlobalISel] Adding FP type information to LLT.

TLDR: We propose modifying LLT by introducing separate integer and floating point kinds to enable non-IEEE floating point types for instruction selection and register bank selection.