LightningCLI save config multifile option required to support save to fsspec filesystem

[mauvilsa]

What does this PR do?

jsonargparse now supports saving config to fsspec filesystem. This is a necessary change for it to work by default.

Fixes #8843

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[codecov]

Codecov Report

Merging #9073 (409be39) into master (856ed10) will decrease coverage by 4%.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master   #9073    +/-   ##
=======================================
- Coverage      93%     89%    -4%     
=======================================
  Files         181     181            
  Lines       15295   15297     +2     
=======================================
- Hits        14211   13596   -615     
- Misses       1084    1701   +617     

[carmocca]

Is this still a draft?

[mauvilsa]

Is this still a draft?

I was waiting for @thecooltechguy to try it out and forgot about it. Will change it to ready for review.