FR: Make jj config edit/path work even if current config is invalid

[Jollywatt]

Is your feature request related to a problem? Please describe.
Consider this scenario: you run jj config edit --user and write some invalid TOML to the config file.
All future jj commands immediately fail because the user config can't be parsed, including jj config edit.

Describe the solution you'd like
I would like the jj config subcommands to not require a working config to run.

Describe alternatives you've considered
The error message contains Hint: Check the config file: <path to config.toml> which you can then open in an editor manually

[yuja]

This was discussed before, and the conclusion was that it wouldn't be simple to add special case for jj config subcommands, and so added a hint instead.

For jj config edit and syntax error, the current idea is to parse edited config file, and if invalid, either restore the original or reopen the editor.
#3905