[IR] Add utility to convert constant expression operands (of an instruction) to instructions.

In the situation where we need to replace a constant operand C from a constant expression CE
by an instruction NI, it not possible without converting CE itself into an instruction. This
utility helps to convert the given set of constant expression operands from an instruction I
into a corresponding set of instructions.

The current use-case for this utility is from the patches - https://reviews.llvm.org/D103225
and https://reviews.llvm.org/D103655.

Reviewed By: rampitec

Differential Revision: https://reviews.llvm.org/D103661