Rename fn_args_layout config option to fn_params_layout

[ayazhafiz]

See #4149 for more details. This change is targeted for rustfmt 2.0.

Closes #4149

[ayazhafiz]

Does the config option need to be guarded behind a flag or will this be cherry-picked for a 2.0 release? If it needs to be behind a flag, I would appreciate some pointers in that 🙂. Thanks!

[calebcartwright]

Thank you for the PR @ayazhafiz!

Does the config option need to be guarded behind a flag

Nope, no worries there. It's a breaking change but we'll be including this change in a major version bump as part of the upcoming rustfmt 2.0 release. It would only require a flag if we were releasing it as part of a minor/patch release for rustfmt 1.x (which we won't be doing).

[calebcartwright]

LGTM, thanks!

@topecongiro - I'll hold off on merging in case you have any thoughts or suggestions on the new config opt name.

[topecongiro]

LGTM.

[karyon]

backport not needed, I believe we can't rename stable configs.

[calebcartwright]

backport not needed, I believe we can't rename stable configs.

We could potentially since there should be a path to a "soft" deprecation where we just print a warning when encountering the option for user awareness, but automatically map the value over to the new option. I think it may be worth reopening #4149 with the extended scope and anyone that wants to work on that could use the commits from here as a building block, and then just add the warning/mapping behavior on top