feat: drop python 3.10 support (#2469)

# What does this PR do?

dropped python3.10, updated pyproject and dependencies, and also removed
some blocks of code with special handling for enum.StrEnum

Closes #2458

Signed-off-by: Charlie Doern <cdoern@redhat.com>

llama_stack/providers/inline/agents/meta_reference/persistence.py

@@ -7,7 +7,7 @@
 import json
 import logging
 import uuid
-from datetime import datetime, timezone
+from datetime import UTC, datetime
 
 from llama_stack.apis.agents import AgentConfig, Session, ToolExecutionStep, Turn
 from llama_stack.distribution.access_control.access_control import AccessDeniedError, is_action_allowed
@@ -47,7 +47,7 @@ class AgentPersistence:
         session_info = AgentSessionInfo(
             session_id=session_id,
             session_name=name,
-            started_at=datetime.now(timezone.utc),
+            started_at=datetime.now(UTC),
             owner=user,
             turns=[],
             identifier=name,  # should this be qualified in any way?