feat(client): add client tool output schema validation and caching (#302)

- Add JSON schema validation for tool call results against output schemas
- Implement automatic tool output schema caching during initialization
- Add `enableCallToolSchemaCaching` configuration option to enable/disable
  schema caching
- Add `JsonSchemaValidator` integration to McpClient builder APIs
- Introduce post-initialization hook mechanism for performing operations
  after successful client initialization
- Cache tool output schemas during `listTools` operations when caching
  is enabled
- Validate tool results against cached schemas in `callTool` operations
- Return error CallToolResult when validation fails
- Add test coverage
- Convert validateToolResult from Mono to synchronous method
- Throw IllegalArgumentException on validation errors

Signed-off-by: Christian Tzolov <christian.tzolov@broadcom.com>

Co-authored-by: Anurag Pant <pantanurag555@github>
Co-authored-by: Christian Tzolov <christian.tzolov@broadcom.com>
Co-authored-by: Daniel Garnier-Moiroux <git@garnier.wf>
Co-authored-by: Dariusz Jędrzejczyk <dariusz.jedrzejczyk@broadcom.com>