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/plugins/manager/testdata/missing-kind-datasource/models.cue

@@ -3,7 +3,7 @@ package grafanaplugin
 import "github.com/grafana/thema"
 
 Query: thema.#Lineage & {
-	name: "missing_slot_impl"
+	name: "missing_kind_datasource"
 	seqs: [
 		{
 			schemas: [

pkg/plugins/manager/testdata/missing-kind-datasource/plugin.json

@@ -1,7 +1,7 @@
 {
   "type": "datasource",
-  "name": "Missing slot impl",
-  "id": "missing-slot-datasource",
+  "name": "Missing kind impl",
+  "id": "missing-kind-datasource",
   "backend": true,
   "state": "alpha",
   "info": {