Upgrade Jetty to 9.4.58.v20250814 and de-aggregate jetty-all (#943)

[slachiewicz]

Forward-port of Jetty 9.4 upgrade and de-aggregation to master.

Fixes #943.

• Replaced jetty-all:9.2.30.v20200428 with org.eclipse.jetty:jetty-bom:9.4.58.v20250814 in root dependency management.
• De-aggregated into modular artifacts (jetty-server, jetty-servlet, jetty-security, jetty-util, jetty-http, jetty-webapp) with appropriate scopes.
• Adapted Jetty 9.4 APIs:
  • Configured UserStore for HashLoginService in HttpWagonTestCase and ServerFixture.
  • Configured BasicAuthenticator explicitly on ConstraintSecurityHandler in ServerFixture.
  • Replaced AbstractSessionManager cookies setup with sessionHandler.setUsingCookies(false).
  • Handled Jetty 9.4 ResourceService precompressed file requirements in HttpWagonTestCase (setting precompressed init parameter and ensuring uncompressed test file is larger than compressed counterpart).
  • Used setStatusWithReason for HTTP error message testing in ErrorWithMessageServlet.