Add Self-Managed install steps to API Orchestration GSG

[akeller]

The Connectors experience for new Self-Managed users is not easy to get started. Users must:

• Know how to start the Connectors runtime without Docker or Helm (Since alpha2, run Camunda as a plain Java app)
• Know how to inject Connectors into Desktop Modeler

Once the Connectors team improves this, DevEx can update the "Get Started with API Orchestration" guide to include Self-Managed steps. For now, this guide will be SaaS only.

Via #3988 (review)

[akeller]

This is in the DevEx backlog as "blocked".

[akeller]

@conceptualshark this should be reworked for C8Run, right? Connectors is included, so we would just need to confirm it works and slot in C8Run similar to the HTO guide. Do you see any blockers I'm missing?

[conceptualshark]

No blockers, but the guide will need to be split again to use Web Modeler for SaaS and Desktop Modeler for C8Run, so the included steps need some updates.

The implication of that split is also interesting - see Eric's comment on the same distinction for the HTO guide - so this should mirror how the HTO guide describes the difference.