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/utils/scheduler.py

@@ -9,7 +9,7 @@ import asyncio
 import functools
 import threading
 from collections.abc import Callable, Coroutine, Iterable
-from datetime import datetime, timezone
+from datetime import UTC, datetime
 from enum import Enum
 from typing import Any, TypeAlias
 
@@ -61,7 +61,7 @@ class Job:
         self._handler = handler
         self._artifacts: list[JobArtifact] = []
         self._logs: list[LogMessage] = []
-        self._state_transitions: list[tuple[datetime, JobStatus]] = [(datetime.now(timezone.utc), JobStatus.new)]
+        self._state_transitions: list[tuple[datetime, JobStatus]] = [(datetime.now(UTC), JobStatus.new)]
 
     @property
     def handler(self) -> JobHandler:
@@ -77,7 +77,7 @@ class Job:
             raise ValueError(f"Job is already in a completed state ({self.status})")
         if self.status == status:
             return
-        self._state_transitions.append((datetime.now(timezone.utc), status))
+        self._state_transitions.append((datetime.now(UTC), status))
 
     @property
     def artifacts(self) -> list[JobArtifact]:
@@ -215,7 +215,7 @@ class Scheduler:
         self._backend = _get_backend_impl(backend)
 
     def _on_log_message_cb(self, job: Job, message: str) -> None:
-        msg = (datetime.now(timezone.utc), message)
+        msg = (datetime.now(UTC), message)
         # At least for the time being, until there's a better way to expose
         # logs to users, log messages on console
         logger.info(f"Job {job.id}: {message}")