feat: add HttpServlet streamable http server transport provider

- Add HttpServletStreamableServerTransportProvider for MCP streamable transport
- Provides HttpServlet equivalent of WebMvcStreamableServerTransportProvider without Spring dependencies
- Supports session management, message replay, graceful shutdown, and async operations
- Add comprehensive integration and unit tests for both sync and async server implementations

This enables MCP server functionality in pure servlet environments without requiring Spring framework dependencies.

Signed-off-by: Christian Tzolov <[email protected]>

Author: tzolov