[Projection tooling] Lay out Factory and Handler types

[stephen-hawley]

As described here, create generic interfaces for factories and handlers.

We will need these pairs for each major type plus variants for some types:

• struct
• frozen struct
• non-blitable struct
• trivial enum
• homogeneous enum
• heterogeneous enum
• class*
• virtual class*
• protocol
• PAT
• actor*

We will need these pairs for each method type plus variants for some types:

• func
• homonymic funcs
• static func
• class func*
• initializer
• failable initializer
• virtual func*
• stored property
• computed property
• indexer

We will need these pairs for each argument type plus variants for some types:

• frozen struct
• non-frozen struct
• non-blitable struct
• trivial enum
• homogeneous enum
• heterogeneous enum
• class/virtual class*
• protocol
• PAT
• actor*
• closure
• tuple