Make class search range larger

[thecrypticace]

After doing an admittedly quite small amount of benchmarking it seems that expanding the search range does have a perf impact but it's not so much of one that we shouldn't increase it. Though this very likely depends on the regex in use.

I've done a few major things in this PR:

• Searching for class lists when hovering now starts at the beginning of the document. This important for users who are using things like cva (the same reason it was expanded for completions in Expand classRegex search range #840)
• The search range for completions inside a class attribute have been expanded to 15k characters. This is useful if you're using a really large cva definition in one class list.
• Ditto for searching for custom regexes which is useful when using CVA with separate variables in a JSX/TSX document.

Fixes #1032
Fixes #984

This is a mostly a stop-gap measure until I can land a better system for "parsing" documents that aims to make most class detection trivial and quite fast.

Custom regexes won't necessarily be able to take advantage of that but if I can get some perf wins elsewhere I might be able to expand the search range even further. Ideally I'd figure out a way to run regexes in a worker thread and allow them to be "cancelled" when they take too long but that is a fairly major-ish undertaking.