Consider moving annotation editor to editor package

[glopesdev]

Currently the enhanced annotation editor is implemented in the Bonsai.Design package. This is not ideal, as it brings in specific dependencies, i.e. Scintilla.NET which end up being unnecessarily propagated to downstream consumers of the design infrastructure.

A better solution would be to have this editor implemented as part of the Bonsai.Editor package, and change the AnnotationBuilder component editor to reference this new editor type; or simply remove the editor attribute altogether and have the component editor be injected via the workflow editor form itself. This would work since the AnnotationBuilder is a known core type which the editor assembly can know about.

[glopesdev]

Alternatively we can investigate switching the dependency to fernandreu/ScintillaNET which provides a .NET 6.0 compatible fork with a published NuGet package.