fix(fmt): preserve comment position in disabled lines

[0xrusowsky]

Motivation

closes #8557

Solution

since we ended up deciding that it was better for solar to use a new SpannedOption<T> which only added the position of uninformed elements, rather than Spanned<T> that would wrap both Some(T) + None and inform their surrounding separators, the fix introduces a workaround that:

1. peeks at a comment before the next item
2. checks if the span from the cursor to the cmnt is disabled
3. gets the snippet from the sourcemap and checks if it has any commas

NOTE: i know we shouldn't rely on the sm, but imo the workaround is acceptable, as this path seems quite unlikely to be triggered frequently

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes