[mlir] replace LLVM dialect float types with built-ins

Continue the convergence between LLVM dialect and built-in types by replacing
the bfloat, half, float and double LLVM dialect types with their built-in
counterparts. At the API level, this is a direct replacement. At the syntax
level, we change the keywords to `bf16`, `f16`, `f32` and `f64`, respectively,
to be compatible with the built-in type syntax. The old keywords can still be
parsed but produce a deprecation warning and will be eventually removed.

Depends On D94178

Reviewed By: mehdi_amini, silvas, antiagainst

Differential Revision: https://reviews.llvm.org/D94179