feat(mcp): resolve absolute and relative message endpoint URIs (#150)

Improve endpoint URI handling by supporting both relative paths
and properly validated absolute URIs.

- Implement URI resolution in HttpClientSseClientTransport:
- Change baseUri field from String to URI type
- Add Utils.resolveUri method to handle both absolute and relative URIs
- Resolve relative URIs against the base URI
- Validate absolute URIs to ensure they match base URI's scheme, authority, and path
- Add parameterized tests for various URI resolution scenarios
- Add ByteBuddy dependency for HttpClient mocking and update Mockito

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