Split PurpleRequestFields into its own files
Review Request #2317 — Created March 5, 2023 and submitted
As before, this uses
hg cp, so it looks like a bunch of deletion.
Again, there's a bit of private API for the cross-struct access, which should go away later.
I also named the file as it will be eventually, even though the class name hasn't been changed.
I did not do any other API changes to make this a simpler review.
Compiled, and opened Request Fields from Demo.