feat: configure backup strategy

[aster-void]

what does this PR allow?

it allows choosing backup strategy from these three:

• move original to backup, create a new file, then move the backup back if it fails / use COPY strategy if the file is hard-link (current behaviour, will be the default)
• copy original to backup, write to the original, then copy the backup back if it fails
• directly write to the original file

why?

some tools such as Vite and Tinymist fails to detect changes because of helix's current backup behaviour. As a workaround, I want to change how helix creates backup.

other things

The diff is subset of #11374, so this can be closed if it gets merged

lmk if there's better name for this, because I'm bad at naming things :)

[TornaxO7]

Is this related to #11374 somehow?

[aster-void]

@TornaxO7 Probably yes.
I just needed a quick patch to not stop my vite watch every other :w's.

I'm willing to change the config variable to something that makes more sense after that PR

[mo8it]

Maybe we should ask @kirawi before proceeding because of the overlap of both PRs. The PR by @kirawi could rebase on top of this one which would also make it smaller and easier to review.

[kirawi]

Sorry, I haven't had a time to look at this yet. I likely won't be able to push the linked PR anytime soon, so I am fine with a knob to choose backup strategy.