build: format codebase imports using ruff linter (#1028)

# What does this PR do?

- Configured ruff linter to automatically fix import sorting issues.
- Set --exit-non-zero-on-fix to ensure non-zero exit code when fixes are
applied.
- Enabled the 'I' selection to focus on import-related linting rules.
- Ran the linter, and formatted all codebase imports accordingly.
- Removed the black dep from the "dev" group since we use ruff

Signed-off-by: Sébastien Han <seb@redhat.com>

[//]: # (If resolving an issue, uncomment and update the line below)
[//]: # (Closes #[issue-number])

## Test Plan
[Describe the tests you ran to verify your changes with result
summaries. *Provide clear instructions so the plan can be easily
re-executed.*]

[//]: # (## Documentation)
[//]: # (- [ ] Added a Changelog entry if the change is significant)

Signed-off-by: Sébastien Han <seb@redhat.com>

llama_stack/apis/agents/agents.py

@@ -15,14 +15,14 @@ from typing import (
     Literal,
     Optional,
     Protocol,
-    runtime_checkable,
     Union,
+    runtime_checkable,
 )
 
 from llama_models.schema_utils import json_schema_type, register_schema, webmethod
 from pydantic import BaseModel, ConfigDict, Field
 
-from llama_stack.apis.common.content_types import ContentDelta, InterleavedContent, URL
+from llama_stack.apis.common.content_types import URL, ContentDelta, InterleavedContent
 from llama_stack.apis.inference import (
     CompletionMessage,
     ResponseFormat,