fix: Remove authorization from provider data (#4161)

# What does this PR do?
- Remove backward compatibility for authorization in mcp_headers
- Enforce authorization must use dedicated parameter
- Add validation error if Authorization found in provider_data headers
- Update test_mcp.py to use authorization parameter
- Update test_mcp_json_schema.py to use authorization parameter
- Update test_tools_with_schemas.py to use authorization parameter
- Update documentation to show the change in the authorization approach

Breaking Change:
- Authorization can no longer be passed via mcp_headers in provider_data
- Users must use the dedicated 'authorization' parameter instead
- Clear error message guides users to the new approach"

## Test Plan
CI

---------

Co-authored-by: Omar Abdelwahab <omara@fb.com>
Co-authored-by: Ashwin Bharambe <ashwin.bharambe@gmail.com>
(cherry picked from commit fe91d331ef)

# Conflicts:
#	src/llama_stack/providers/remote/tool_runtime/model_context_protocol/model_context_protocol.py
#	tests/integration/inference/test_tools_with_schemas.py
#	tests/integration/tool_runtime/test_mcp.py
#	tests/integration/tool_runtime/test_mcp_json_schema.py

tests/integration/inference/test_tools_with_schemas.py

@@ -9,8 +9,6 @@ Integration tests for inference/chat completion with JSON Schema-based tools.
 Tests that tools pass through correctly to various LLM providers.
 """
 
-import json
-
 import pytest
 
 from llama_stack import LlamaStackAsLibraryClient
@@ -193,15 +191,19 @@ class TestMCPToolsInChatCompletion:
             mcp_endpoint=dict(uri=uri),
         )
 
+<<<<<<< HEAD
         provider_data = {"mcp_headers": {uri: {"Authorization": f"Bearer {AUTH_TOKEN}"}}}
         auth_headers = {
             "X-LlamaStack-Provider-Data": json.dumps(provider_data),
         }
 
+=======
+        # Use the dedicated authorization parameter
+>>>>>>> fe91d331 (fix: Remove authorization from provider data (#4161))
         # Get the tools from MCP
         tools_response = llama_stack_client.tool_runtime.list_tools(
             tool_group_id=test_toolgroup_id,
-            extra_headers=auth_headers,
+            authorization=AUTH_TOKEN,
         )
 
         # Convert to OpenAI format for inference