Introduce RoundOp in the math dialect. The operation rounds the operand to the
nearest integer value in floating-point format. RoundOp lowers to LLVM
intrinsics 'llvm.intr.round' or as a function call to libm (round or roundf).
Reviewed By: ftynse
Differential Revision: https://reviews.llvm.org/D127286
libm doesn't have overloads for the small types, so promote them to a
bigger type and use the f32 function.
Differential Revision: https://reviews.llvm.org/D125093
Precursor: https://reviews.llvm.org/D110200
Removed redundant ops from the standard dialect that were moved to the
`arith` or `math` dialects.
Renamed all instances of operations in the codebase and in tests.
Reviewed By: rriddle, jpienaar
Differential Revision: https://reviews.llvm.org/D110797
