[IROutliner] Ensure that phi values that are passed in as arguments are remapped as arguments

Issue: https://github.com/llvm/llvm-project/issues/54430

For incoming values of phi nodes added to an outlined function to accommodate different exit paths in the function, when a value is a constant that is passed into the outlined function as an argument, we find the corresponding value in the first extracted function used to fill the overall outlined function. When this value is an argument, the corresponding value used will be the old value, prior to outlining. This patch maintains a mapping from these values to arguments, and uses this mapping to update the added phi node accordingly.

Reviewers: paquette

Recommit of d6eb480a

Differential Revision: https://reviews.llvm.org/D122206