New AI Agent Task / AI Agent Sub-process connector types and element templates (v2)

[maff]

Is your feature request related to a problem? Please describe.

The current AI Agent connector type identifiers (io.camunda.agenticai:aiagent:1, io.camunda.agenticai:aiagent-job-worker:1) and element template structure carry historical baggage that blocks the clean introduction of new providers, backends, and API families.

Describe the solution you'd like

Introduce new connector types and element templates for the AI Agent:

What	Task	Sub-process
Connector type / Zeebe job type	io.camunda.agenticai:aiagent-task:2	io.camunda.agenticai:aiagent-subprocess:2
Element template ID	io.camunda.connectors.agenticai.aiagent.task.v2	io.camunda.connectors.agenticai.aiagent.subprocess.v2
Element template filename	agenticai-aiagent-task.json	agenticai-aiagent-subprocess.json
Display name	AI Agent Task	AI Agent Sub-process

The new templates expose the new ProviderConfiguration shape: one provider entry per wire format, with backend and apiFamily dropdowns and conditional auth fields. Update the element-templates/README.md index and move the previous templates into element-templates/versioned/ per the existing pattern.

Old connector types stay available but are handled by a separate input-rewrite shim issue.

Describe alternatives you've considered

Bumping the existing templates again carries forward the legacy name ("job-worker") and the legacy provider structure; we'd accumulate template versions instead of getting the structural reset.

Additional context