Extend configurator to provide fully customisable workshop experience

[holly-cummins]

Follow-up to #253.

Here are some next steps:

• [X] Use an iteration plugin in the docs plugin so that the tailoring can scale to more parameters without a combinatoric pom-splosion of manually crafted variations (#343)
• [ ] Add a header or something equivalent to indicate what kind of config a page is using
• [X] Update the UI to allow two-tier configuration (we preset some parameters and then users select OS, etc), maybe with query parameters and a 'hide query params' flag (also in #343, via query params)
• [X] Extend the parameterisation to the Azure files and spine, to get rid of the azure spine.html and maybe even the azure introduction (#302)
• [ ] Extend to gradle (https://github.com/quarkusio/quarkus-workshops/issues/240), as another knob
• [ ] Add a knob for 'workshop length', building on #296, and also #382
• [ ] Add a mini-configurator in the ToC so that if people end up on the wrong doc they have a pathway to make it right
• [ ] Maybe use asciidoctor-tabs to add tabs into the 'all-options' doc
• [ ] Where we have a bulleted list and only one option, tidy that up
• [ ] Improve scalability so we don't exponentially increase docs build time with each new variant (#384)
• [ ] In the configurator, when someone clicks a button, update the URI query parameters, so they can copy-paste a URL for their configuration

[agoncal]

@holly-cummins and what about the use_observability, use_messaging and use_extension options ? They are not in https://quarkus.io/quarkus-workshops/super-heroes yet. Later ?

[agoncal]

Sorry, didn't see https://github.com/quarkusio/quarkus-workshops/pull/354

[holly-cummins]

Yeah, I took them out while I was struggling with build performance/archive size. I did the change to put them back in but thought I'd wait to merge until after the workshop in case we want to push through any hasty changes. They seem to add about 7m to the build time, so not catastrophic, but also perhaps not what we want right now.