lsp: Identify language servers by their configuration (#35270)

- **WIP: reorganize dispositions**
- **Introduce a LocalToolchainStore trait and use it for LspAdapter
methods**

Closes #35782
Closes #27331

Release Notes:

- Python: Improved propagation of a selected virtual environment into
the LSP configuration. This should the make all language-related
features such as Go to definition or Find all references more reliable.

---------

Co-authored-by: Cole Miller <cole@zed.dev>
Co-authored-by: Lukas Wirth <lukas@zed.dev>

crates/language_extension/src/language_extension.rs

@@ -52,7 +52,7 @@ impl ExtensionLanguageProxy for LanguageServerRegistryProxy {
         load: Arc<dyn Fn() -> Result<LoadedLanguage> + Send + Sync + 'static>,
     ) {
         self.language_registry
-            .register_language(language, grammar, matcher, hidden, load);
+            .register_language(language, grammar, matcher, hidden, None, load);
     }
 
     fn remove_languages(