Review Automation contributions merge/removal/enablement features

With NXP-29984, automation extension points where migrated to runtime registries.

Review the following contributions to see if the current status can be improved:

Extension points "org.nuxeo.ecm.automation.core.AutomationComponent-chains" and "org.nuxeo.ecm.automation.core.AutomationComponent-operations" require an explicit "replace" attribute for override (there is no merge support anyway).
This is not the case for extension point "org.nuxeo.automation.scripting.internals.AutomationScriptingComponent--operation" which could be confusing for Studio configuration.

Also, enablement and removal are not currently supported: maybe corresponding boolean on XRegistry annotations should be changed to "true" for these features to be natively covered.

Check also alias behaviour, causing misbehaviour on explorer side (NXP-30203: the new name might be better moved to an alias)