Fix toolchain detection for worktree-local paths (#20229)

Reimplements `pet::EnvironmentApi`, trying to access the `project_env`
first
Closes #20177 

Release Notes:

- Fixed python toolchain detection when worktree local path is set

crates/remote_server/src/headless_project.rs

@@ -108,8 +108,14 @@ impl HeadlessProject {
             observer.shared(SSH_PROJECT_ID, session.clone().into(), cx);
             observer
         });
-        let toolchain_store =
-            cx.new_model(|cx| ToolchainStore::local(languages.clone(), worktree_store.clone(), cx));
+        let toolchain_store = cx.new_model(|cx| {
+            ToolchainStore::local(
+                languages.clone(),
+                worktree_store.clone(),
+                environment.clone(),
+                cx,
+            )
+        });
         let lsp_store = cx.new_model(|cx| {
             let mut lsp_store = LspStore::new_local(
                 buffer_store.clone(),