input: Skip highlighting for plain text and unregistered languages

[zanmato]

Closes #2566

Description

Plain text and other unregistered languages, like a code fence in markdown, falls back to JSON currently. Which is a lot of unnecessary parsing, and also causes quite a big memory overhead.

Screenshot

Before	After

How to Test

• Generate a big text file

(for i in $(seq 1 999999); do echo 'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.'; done) > big_lorem.txt

• Disable linter and color provider in the editor

--- a/crates/story/examples/editor.rs
+++ b/crates/story/examples/editor.rs
@@ -713,7 +713,7 @@ impl Example {
             editor.lsp.code_action_providers = vec![lsp_store.clone(), Rc::new(TextConvertor)];
             editor.lsp.hover_provider = Some(lsp_store.clone());
             editor.lsp.definition_provider = Some(lsp_store.clone());
-            editor.lsp.document_color_provider = Some(lsp_store.clone());
+            // editor.lsp.document_color_provider = Some(lsp_store.clone());
 
             editor
         });
@@ -731,7 +731,7 @@ impl Example {
         Self::load_files(tree_state.clone(), PathBuf::from("./"), cx);
 
         let _subscriptions = vec![cx.subscribe(&editor, |this, _editor, _: &InputEvent, cx| {
-            this.lint_document(cx);
+            // this.lint_document(cx);
         })];
 
         Self {

• Run the editor example, open the big text file and compare memory usage

I've also checked various other files in the editor example

Checklist

• I have read the CONTRIBUTING document and followed the guidelines.
• Reviewed the changes in this PR and confirmed AI generated code (If any) is accurate.
• Passed cargo run for story tests related to the changes.
• Tested macOS, Windows and Linux platforms performance (if the change is platform-specific)

[huacnlee]

Here we can use debug_assert!

[zanmato]

Replaced it with debug_assert

[zanmato]

Removed the added matches! instead and just return the new plain config in the original match