Synchronize the names for RequiredParam<T> arguments in header files

[dsnopek]

This is a follow-up to #113282

That PR changed the argument names in the .cpp files, but not the .h files. This updates the .h files to match!

Since it's only changing the names in the headers files, it shouldn't carry any risk. (But sorry for the extra churn!)

[Ivorforce]

The main reason I think the parameter name prefixes should match across the files is that it makes it slightly easier to global-search the function signature.
Otherwise, I don't feel very strongly about this.

[akien-mga]

Thanks!