Use outline queries to chunk files syntactically (#11283)

This chunking strategy uses the existing `outline` query to chunk files.
We try to find chunk boundaries that are:

* at starts or ends of lines
* nested within as few outline items as possible

Release Notes:

- N/A

crates/language/src/language.rs

@@ -55,10 +55,10 @@ use std::{
         Arc,
     },
 };
-use syntax_map::SyntaxSnapshot;
+use syntax_map::{QueryCursorHandle, SyntaxSnapshot};
 pub use task_context::{BasicContextProvider, ContextProvider, ContextProviderWithTasks};
 use theme::SyntaxTheme;
-use tree_sitter::{self, wasmtime, Query, WasmStore};
+use tree_sitter::{self, wasmtime, Query, QueryCursor, WasmStore};
 use util::http::HttpClient;
 
 pub use buffer::Operation;
@@ -101,6 +101,15 @@ where
     })
 }
 
+pub fn with_query_cursor<F, R>(func: F) -> R
+where
+    F: FnOnce(&mut QueryCursor) -> R,
+{
+    use std::ops::DerefMut;
+    let mut cursor = QueryCursorHandle::new();
+    func(cursor.deref_mut())
+}
+
 lazy_static! {
     static ref NEXT_LANGUAGE_ID: AtomicUsize = Default::default();
     static ref NEXT_GRAMMAR_ID: AtomicUsize = Default::default();