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This fixes the loading and unloading of plugins via the "Extensions"
section of the preferences window.

The previous functionality was lost during the refactor of Builder
for 3.34.

Fixes #1193

This ensures we have the appropriate version before plugins call into any
gi loading.

This moves the application code into the location of the upcoming
libide-gui static library. Some notable changes as part of the refactor
include cleanup to how command line actions are processed.

Furthermore, we'll see in upcoming commits how workbenches have been
abstracted into a WindowGroup to allow for multi-window work areas that
contain workspaces (window).