Support Python 3.10+ (on CI) and remove redundant Self imports (#2553)

* ci(workflows): add Python version matrix (3.10-3.12) for tests

* refactor: remove explicit Self import from typing

Python 3.10+ natively supports Self type annotation without explicit imports

* chore: rename external_memory file test

---------

Co-authored-by: Lorenze Jay <63378463+lorenzejay@users.noreply.github.com>

src/crewai/memory/memory.py

@@ -1,4 +1,4 @@
-from typing import Any, Dict, List, Optional, Self
+from typing import Any, Dict, List, Optional
 
 from pydantic import BaseModel
 
@@ -38,6 +38,6 @@ class Memory(BaseModel):
             query=query, limit=limit, score_threshold=score_threshold
         )
 
-    def set_crew(self, crew: Any) -> Self:
+    def set_crew(self, crew: Any) -> "Memory":
         self.crew = crew
         return self