Add getEnclosingFunction logic for range expansion in edits + chats (and possibly other commands)

[umpox]

What:

• Edits and Chats currently expand a cursor position to the nearest folding range. This is ok, but it isn’t ideal, there are many cases where this fails for us. For example, an “it” block inside a “describe” block in a JS test is not seen as a folding range, so we always expand the selection to the full “describe” block.
• Ideally we can always expand to the nearest enclosing function if available, before falling back to the folding range logic.

How:

• Add a tree-sitter query to find the nearest enclosing function
• Update our Smart Selection logic to look for this first.
• This should automatically add this behaviour to chat and edit.

[chillatom]

Adding an issues that I hope this might address. Where the user cursor is within a massive class, we throw an error saying "selected text is too long", would be nice to gracefully handle that.

https://sourcegraph.slack.com/archives/C05AGQYD528/p1711134734677989

[umpox]

Closed by #3507