Add MCP tools for Chronicle REST API Case Creation Endpoints

[dandye]

Implemented MCP tools for Chronicle REST API case creation endpoints (create_case, create_manual_case, and create_or_update_case) using the v1alpha API in secops_mcp/tools/case_management.py. Added comprehensive unit tests in tests/test_case_management_tools.py.

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PR created automatically by Jules for task 8503933169267217566 started by @dandye

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