debugger: Ensure that Python's adapter work dir exists (#35618)

Closes #ISSUE

cc @Sansui233 who triaged this in
https://github.com/zed-industries/zed/issues/35388#issuecomment-3146977431
Release Notes:

- debugger: Fixed an issue where a Python debug adapter could not be
installed when debugging Python projects for the first time.

crates/dap_adapters/src/python.rs

@@ -101,6 +101,9 @@ impl PythonDebugAdapter {
             .await
             .context("Could not find Python installation for DebugPy")?;
         let work_dir = debug_adapters_dir().join(Self::ADAPTER_NAME);
+        if !work_dir.exists() {
+            std::fs::create_dir_all(&work_dir)?;
+        }
         let mut path = work_dir.clone();
         path.push("debugpy-venv");
         if !path.exists() {