Kindsys: Remove defs, Slot->SchemaInterface (#61069)

* kindsys: Remove defs, Slot->SchemaInterface

* Remove excess file

* Fix up tests

* Regenerate kinds report

* Final bits of cleanup

* Stop complaining, linter

* Update pkg/kindsys/kindcat_composable.cue

Co-authored-by: Tania <yalyna.ts@gmail.com>

Co-authored-by: Tania <yalyna.ts@gmail.com>

pkg/codegen/tmpl.go

@@ -38,7 +38,6 @@ type (
 	}
 	tvars_kind_registry struct {
 		// Header tvars_autogen_header
-		NumStructured     int
 		PackageName       string
 		KindPackagePrefix string
 		Kinds             []*DeclForGen