Fix OpenAPI UI options processing

[tjquinno]

Resolves #5998

Changes:

1. The original OpenApiUiFull.Builder#convertOptions method (now renamed to uiOptions) prematurely exited a loop when processing UI options.
2. Originally OpenApiUiFull.Builder kept its own Map<Options, String>. It now reuses the Map<String, String> kept by its abstract superclass OpenApiUIBase.Builder to avoid confusion and converts when needed. The change in the type of the key in the map also involves two slight changes in retrieving the url entry from the map for a sanity check warning.
3. There was redundant and confusing config logic in the abstract builder superclass and the builder in OpenApiUiFull.
4. Expand the UI config test to make sure multiple overridden values are applied correctly.

Signed-off-by: [email protected] [email protected]