Proposal for Registration rework

[CedNaru]

Here the list of actions as discussed with Cedric in our call:

• No more bootstrap for the editor.
• A single user bootstrap per project.
• Bootstrap.kt should define 2 functions: InitLibrary() and LoadUserScripts(Jarpath: String).

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• Rework the API for registration (make manual registration easier for other languages like Scala and Clojure).
• Get rid of Entry and Context. Instead, use a Registrar interface and search its implementations with ServiceLoader.

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• Adding gradle option to grab additionnal jars and put them in the shadow jar.
• Adding exclude filter in the export plugin for jars.

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• Add a detection of bootstrap changes and make a prompt appear that ask the users to restart the engine.
• Move the .gdj generation from gradle plugin to godot editor.
• Add option to disable automatic registration (optional, enabled by default).