Skip over folded regions when iterating over multibuffer chunks (#15646)

This commit weaves through new APIs for language::BufferChunks, multi_buffer::MultiBufferChunks and inlay_map::InlayChunks that allow seeking with an upper-bound. This allows us to omit doing syntax highligting and looking up diagnostics for folded ranges. This in turn directly improves performance of assistant panel with large contexts.

Release Notes:

- Fixed poor performance when editing in the assistant panel after
inserting large files using slash commands

---------

Co-authored-by: Max <max@zed.dev>
Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>

crates/language/src/language.rs

@@ -1341,7 +1341,7 @@ impl Language {
                 });
             let highlight_maps = vec![grammar.highlight_map()];
             let mut offset = 0;
-            for chunk in BufferChunks::new(text, range, Some((captures, highlight_maps)), vec![]) {
+            for chunk in BufferChunks::new(text, range, Some((captures, highlight_maps)), None) {
                 let end_offset = offset + chunk.text.len();
                 if let Some(highlight_id) = chunk.syntax_highlight_id {
                     if !highlight_id.is_default() {