Avoid the accidental removal of comments inside expressions by dx fmt

[jjvn84]

This PR modifies the behaviour of dx fmt to add back comments removed from expressions when parsing the code to reformat it. It should only affect expressions used in attributes for rsx elements.

Fixes #2524

[jkelleyrtp]

Thanks for the PR!

I just opened a similar PR to fix whitespace removal from the end of rsx blocks here:

#4423

Hopefully with these two PRs all whitespace should be handled properly!

[jkelleyrtp]

Ended up adding a few more test cases and inverting the line pull logic to pull whitespace on top of pretty lines instead of pretty lines under whitespace.

Thanks for the really clever solution here - been something I've been meaning to fix for a long time and it was nice to see a PR popup fixing it :)