CLI Commands: Fix design-time assembly resolution

[bricelam]

Resolves #3925

Provider writers beware, this splits DesignTimeProviderServicesAttribute.FullyQualifiedTypeName into TypeName and AssemblyName. (cc @rowanmiller)

This should also fix #3862

[lajones]

But maybe talk to @ajcvickers first - he raised #3111 which was to do the opposite and combine TypeName and AssemblyName.

[bricelam]

The choices were...

• Undo Use fully qualified assembly name in DesignTimeProviderServicesAttribute #3111
• Parse FullyQualifiedTypeName

I went with the simplest option. 😉 I'll bring it up in triage.

[ErikEJ]

@bricelam Does this mean I should strong sign the SQL CE provider?

[bricelam]

@ErikEJ No, it should still be optional.