Add basic PyEnv and pixi support for python environments (#37156)

cc https://github.com/zed-industries/zed/issues/29807

Release Notes:

- Fixed terminals and tasks not respecting python pyenv and pixi
environments

crates/project/src/project_tests.rs

@@ -40,7 +40,7 @@ use serde_json::json;
 #[cfg(not(windows))]
 use std::os;
 use std::{env, mem, num::NonZeroU32, ops::Range, str::FromStr, sync::OnceLock, task::Poll};
-use task::{ResolvedTask, TaskContext};
+use task::{ResolvedTask, ShellKind, TaskContext};
 use unindent::Unindent as _;
 use util::{
     TryFutureExt as _, assert_set_eq, maybe, path,
@@ -9222,8 +9222,8 @@ fn python_lang(fs: Arc<FakeFs>) -> Arc<Language> {
         fn manifest_name(&self) -> ManifestName {
             SharedString::new_static("pyproject.toml").into()
         }
-        async fn activation_script(&self, _: &Toolchain, _: &dyn Fs) -> Option<String> {
-            None
+        async fn activation_script(&self, _: &Toolchain, _: ShellKind, _: &dyn Fs) -> Vec<String> {
+            vec![]
         }
     }
     Arc::new(