Editor rewrite: clean up sdpkg management workflow

Is your feature request related to a problem? Please describe.
Having to manually edit packages (i.e. sdpkg files) has always been a bit of a pain.

Describe the solution you'd like
See above. Would be nice to have a function in the new editor to clean up this workflow a bit; maybe a Package Editor that can be accessed from the solution explorer for each project with an sdpkg that allows for more intuitive management and editing of the underlying yaml. Could use list edit controls for the bits of yaml that could be interpreted as lists, maybe a custom control for the Bundles nested list if in can be confirmed that the asset bundler works again.

Describe alternatives you've considered
Alternatively;

• Treat sdpkg as an asset that can be edited from the inspector, like we do for other serialised yaml assets.

Additional context

Start by examining the new editor's solution explorer and inspector handling for serialized YAML assets, then trace how each project's sdpkg and its Bundles list are currently managed. The issue presents several possible designs rather than a defined entry point or test; done criteria would need to specify the chosen editing workflow and supported sdpkg fields.