project search: Stream search results to improve TTFB (#16923)

This is a prototype change to improve latency of local project searches.
It refactors the matcher to keep paths "in-order" so that we don't need
to wait for all matching files to display the first result.

On a test (searching for `<` in zed.dev) it changes the time until first
result from about 2s to about 50ms. The tail latency seems to increase
slightly (from 5s to 7s) so we may want to do more tuning before hitting
merge.

Release Notes:

- reduces latency for first project search result

---------

Co-authored-by: Thorsten Ball <mrnugget@gmail.com>
Co-authored-by: Antonio <antonio@zed.dev>
Co-authored-by: Thorsten <thorsten@zed.dev>

crates/project/src/search.rs

@@ -420,6 +420,11 @@ impl SearchQuery {
         self.as_inner().files_to_exclude()
     }
 
+    pub fn filters_path(&self) -> bool {
+        !(self.files_to_exclude().sources().is_empty()
+            && self.files_to_include().sources().is_empty())
+    }
+
     pub fn file_matches(&self, file_path: Option<&Path>) -> bool {
         match file_path {
             Some(file_path) => {