Decorator for Node GUIs and GUI deferred loading

[HeftyCoder]

This PR introduces a new way to assign Node GUIs to Nodes. Specifically:

• It introduces a decorator called node_gui which accepts a Node as a parameter. Assigning a gui to a node happens in the gui.py file and not the nodes.py, allowing for IDE hinting and deprecating the need for the import_guis and export_guis functions.
• Introduces a on_gui_load function which can be applied to any function in the imported nodes.py file. This function will then be called after package loading in import_nodes_package.
• Adds a api.py file in the ryven folder. Might not be needed, but thought it was a good idea. Bad idea, read the conversation for details.

The built_in package and the pkg_test package (which has linalg and std subpackages) have been changed to use this new utility. The older linalg and std packages haven't been altered and are working with the "deprecated" functions.

CC: these ideas were first discussed in #171 as a result of investigating sub-packages

[leon-thomm]

Please correct me if I'm missing something but I think your api.py compromises the whole point of separating nodes dependencies and UI dependencies in the first place, which is that Ryven has a headless mode in which it runs without any Qt dependencies (only ryvencore).

[leon-thomm]

Clarifying the previous comment: Ryven can run in environments where Qt is not even installed (because it can't without desktop environment). That's why ryven.main is separate from ryven.gui. [^1] ryven.main.Ryven.run() runs with the editor, ryven.main.RyvenConsole.run() runs without.

[^1]: config.py imports something from gui but it doesn't cause Qt import

[leon-thomm]

I took the liberty to fix the imports and remove api. If I messed up your local branch I can rollback re-commit later. Looks good to me now, anything else from your side?

[HeftyCoder]

I think your api.py compromises the whole point of separating nodes dependencies and UI dependencies in the first place

I was (and probably still am) confused about how python importing works. I thought that by calling from ryven.api import in_gui_mode only that function would be imported, ignoring the rest. Didn't account that in_gui_mode was also imported in gui_env. I thought one could bundle everything that way. My bad.

I made minor changes to the consume_last_exported_package function. Other than that, I'm good!

[leon-thomm]

Importing a module just means running it. A module-level expression such as def foo makes the foo symbol available. A module-level expression such as import ryven.gui_env runs ryven.gui_env at the point where the import is stated. A from import is actually no different, from ryven.api import in_gui_mode will first run ryven.api and then make in_gui_mode available locally. That's why it matters how imports are placed.