[Feature Request]: Allow environmental variable to control "Enabled" checkbox in asynchronous webservices (metadata)

### What would you like to happen?

Follow-up of https://github.com/apache/hop/issues/5628.

For metadata object "Asynchronous Web Service" we would like to be able to control the "Enabled" checkbox via an environmental variable:

Documentation would include valid values for this variable, and the logic that is applied when the variable is empty/unset, or contains invalid values.
Similary, what would happen when the checkbox conflicts with the value of the variable.
Optimally, the checkbox would be greyed out when the config variable is used?

### Issue Priority

Priority: 3

### Issue Component

Component: Hop Gui, Component: Metadata

Start by locating the Asynchronous Web Service metadata configuration and its Hop GUI editor, then trace how the Enabled checkbox is currently read and persisted. Define the environment-variable values, empty or invalid behavior, precedence when it conflicts with the checkbox, and the expected documentation and GUI state.

Written by the indexing model from the issue text.