MP rest client cannot use generic interfaces

Having an interface

```
interface ViewResource {
@GET
@Path("{id}")
@Produces(APPLICATION_JSON)
V get(@PathParam("id") UUID id);
}
```

... then defining

```
@Path("employee")
interface EmployeeResource extends ViewResource {
}
```

... I try to use the interface `EmployeeResource` as a MP rest client. Building the client fails with the following exception

```
Exception in thread "main" java.lang.IllegalArgumentException: Type parameter V not a class or parameterized type whose raw type is a class
at javax.ws.rs.core.GenericType.getClass(GenericType.java:179)
at javax.ws.rs.core.GenericType.(GenericType.java:136)
at org.glassfish.jersey.microprofile.restclient.MethodModel$Builder.returnType(MethodModel.java:561)
at org.glassfish.jersey.microprofile.restclient.MethodModel$Builder.build(MethodModel.java:631)
at org.glassfish.jersey.microprofile.restclient.MethodModel.from(MethodModel.java:107)
at org.glassfish.jersey.microprofile.restclient.RestClientModel.parseMethodModels(RestClientModel.java:113)
at org.glassfish.jersey.microprofile.restclient.RestClientModel.from(RestClientModel.java:70)
at org.glassfish.jersey.microprofile.restclient.RestClientBuilderImpl.build(RestClientBuilderImpl.java:195)
```

Jersey Server is able to use this generic approach (i.e. implement a generic `ViewResourceBase` then a `EmploymentResourceImpl`.

Also the MP rest client from `RestEasy` simply works.

See [this project](https://github.com/pa314159/jersey-mp-generic) that demonstrates the issue. I also have a fix on [this branch](https://github.com/pa314159/jersey/tree/generic-return-type) that uses `geantyref`.

Let me know if you want to create a PR based on it or if you want an independent fix.

Start with the linked demonstration project and trace the failure through org.glassfish.jersey.microprofile.restclient.MethodModel.Builder.returnType, RestClientModel, and RestClientBuilderImpl. Compare the proposed generic-return-type branch and verify that an EmployeeResource extending ViewResource can build and invoke the MP REST client without the GenericType exception.

Written by the indexing model from the issue text.