[#31926] [java] call provision service when creating external workers.

[lostluck]

This fixes metrics from the Java SDK when running in Loopback mode against Prism (and probably a few other usecases too).

• The Provision API is usually called by the container bootloader to initialize the worker.
• Without calling the ProvisionAPI, the worker doesn't know a runner's capabilities.
• This lead to the Java SDK to send old style metrics in loopback mode, which prism doesn't support.
• That meant there were no metrics being propagated at in the UI.

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[lostluck]

R: @damondouglas

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