[InstSimplify][InstCombine] Remove unnecessary `m_c_*` matchers. (#81712)

This patch removes unnecessary `m_c_*` matchers since we always
canonicalize `commutive_op Cst, X` into `commutive_op X, Cst`.

Compile-time impact:
https://llvm-compile-time-tracker.com/compare.php?from=bfc0b7c6891896ee8e9818f22800472510093864&to=d27b058bb9acaa43d3cadbf3cd889e8f79e5c634&stat=instructions:u