Support OAS servers URLs and some general fixes

[tarilabs]

As the title says.
If/once approved, I will cherry-pick to backport to 2.0.x branch too.

Demo 1 (no OAS servers defined)

If the OAS descriptors does not provide a servers, the application will not present any specific changes

In this example a simple Quarkus based app:

as before:

Demo 2 (the OAS descriptors define servers)

If the OAS descriptor defines servers URLs, those are selectable via dropdown-box.

In this example a simple kie-server based container:

provides in the OAS descriptor some servers URLs, hence that is used to address the POST request:

Details:

[MikeEdgar]

Thanks @tarilabs - this looks good.