fix(orchestrator): endless onChange() loop and turning ui:allowNewItems from string to boolean type

[mareklibra]

Multiple small changes at once:

• fix for an infinite onChange() loop by ActiveDropdown().
• use generic readOnly instead of proprietary ui:readonly - https://json-schema.org/understanding-json-schema/keywords#readonly
• the ui:allowNewItems property became boolean (instead of string)

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Example of use: rhdhorchestrator/orchestrator-demo#72

[rhdh-gh-app]

Changed Packages

Package Name	Package Path	Changeset Bump	Current Version
@red-hat-developer-hub/backstage-plugin-orchestrator-form-react	workspaces/orchestrator/plugins/orchestrator-form-react	patch	v2.3.0
@red-hat-developer-hub/backstage-plugin-orchestrator-form-widgets	workspaces/orchestrator/plugins/orchestrator-form-widgets	patch	v1.4.0

[sonarqubecloud]

Quality Gate failed

Failed conditions
D Reliability Rating on New Code (required ≥ A)

See analysis details on SonarQube Cloud

Catch issues before they fail your Quality Gate with our IDE extension SonarQube for IDE

[mareklibra]

The SonarCloud finding is about using Array.sort() to compare two arrays while ignoring items order.
This is a common technique, so I would ignore that finding unless there is strong opinion against.

[gciavarrini]

lgtm