Check if ModuleCancellationInstrumenter gracefully handles ref kind differences between original and replacement methods

[RikkiGibson]

I am wondering if any unexpected behavior changes could occur if:

• the original method was a readonly struct method and the replacement method was not, for example.
• Or, the other way around, the original is non-readonly and the replacement is readonly.

Since it seems like we are not checking the readonly-ness of the this parameter in these checks.

Since this PR is already merged some time ago, I will open a new issue based on this comment.

Originally posted by @RikkiGibson in #71896 (comment)

[RikkiGibson]

@tmat