python: Re-land usage of source file path in toolchain picker (#31893)

This reverts commit 1e55e88c18.

Closes #ISSUE

Release Notes:

- Python toolchain selector now uses path to the closest pyproject.toml
as a basis for picking a toolchain. All files under the same
pyproject.toml (in filesystem hierarchy) will share a single virtual
environment. It is possible to have multiple Python virtual environments
selected for disjoint parts of the same project.

crates/language/src/manifest.rs

@@ -1,8 +1,7 @@
 use std::{borrow::Borrow, path::Path, sync::Arc};
 
 use gpui::SharedString;
-
-use crate::LspAdapterDelegate;
+use settings::WorktreeId;
 
 #[derive(Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
 pub struct ManifestName(SharedString);
@@ -39,10 +38,15 @@ pub struct ManifestQuery {
     /// Path to the file, relative to worktree root.
     pub path: Arc<Path>,
     pub depth: usize,
-    pub delegate: Arc<dyn LspAdapterDelegate>,
+    pub delegate: Arc<dyn ManifestDelegate>,
 }
 
 pub trait ManifestProvider {
     fn name(&self) -> ManifestName;
     fn search(&self, query: ManifestQuery) -> Option<Arc<Path>>;
 }
+
+pub trait ManifestDelegate: Send + Sync {
+    fn worktree_id(&self) -> WorktreeId;
+    fn exists(&self, path: &Path, is_dir: Option<bool>) -> bool;
+}