Un-flatten LSP symbol picker with a tree view.

[weakphish]

LSP supports hierarchical symbols, but helix currently flattens then into a list and shows them with space+s. We could reuse the tree view that will soon be merged with the file tree (#2377) to display the symbol information in a tree interface.

Another option is to use tree sitter tags instead of LSP (not sure if it can report hierarchical information).

Originally posted by @sudormrfbin in #2425 (comment)

Another idea that I would like to explore is adding NerdFont symbols optionally to add a bit of visual flavor. This would be opt-in through an explicit TOML configuration.

[pascalkuthe]

Discussed with @the-mikedavis . A tree view doesn't work well with the picker because fuzzy matching always resortd the list (and isn't super useful when it doesn't). In general tree doesn't really fit in with the picker.

Thisbkind of feature would require a dedicated ui like discussed in #2425 . Closing in favor of that issue