save-analysis: adjust `process_formals` wrt. or-patterns

[Centril]

Filing this as a keep-sake for discussion in #64250 (comment).

cc @Xanewok

[Centril]

@Xanewok Or-patterns are "fleshed out" now... ;)

[varkor]

@Xanewok: do you know if is this still an issue?

[Xanewok]

From what I know, this still needs to be fixed, yes.

[jyn514]

Save-analysis has been removed from the compiler.