[REQ] Add support for Helidon SE clients and servers; improve support for Helidon MP

Created by: tjquinno

Is your feature request related to a problem? Please describe.

Helidon is currently supported via the java/jaxrs-spec generator and library and, to some extent, by the MicroProfile client generator.

Support in the generator for Helidon MP could be made quite a bit better, and support for Helidon SE is absent.

Describe the solution you'd like

Add support for Helidon SE client and servers and improve the support for Helidon MP clients and servers. Do so by adding Helidon-specific generators.

Describe alternatives you've considered

Enhancing existing generators to add the requested support would complicate those generators significantly and risk introducing bugs into support for other targets.

Additional context

Support for other platforms has also taken the form of specific generators for them. The Helidon team is happy to do the work to create Helidon-focused generators.