[flang][hlfir] inline hlfir.transpose as hlfir.elemental

[flang][hlfir] inline hlfir.transpose as hlfir.elemental

Inlining as a hlfir.elemental will allow the transpose to be inlined
into subsequent operations in some cases. For example,

y = TRANSPOSE(x)
z = y * 2

Will operate in a single loop without creating a temporary for the
TRANSPOSE (unlike the runtime call, which always allocates).

This is in a new SimplifyHLFIRIntriniscs pass. The intention is that some
day that pass might replace the FIR SimplifyIntrinsics pass.

Depends On: D149060

Reviewed By: jeanPerier, vzakhari

Differential Revision: https://reviews.llvm.org/D149067