schema: Migrate from scuemata to thema (#49805)

* Remove crufty scuemata bits

Buhbye to: cue/ dir with old definitions, CI steps for checking unnecessary
things, and the original dashboard scuemata file.

* Remove grafana-cli cue subcommand

* Remove old testdata

* Don't swallow errors from codegen

* Small nits and tweaks to cuectx package

* WIP - refactor pluggen to use Thema

Also consolidate the embed.FS in the repo root.

* Finish halfway rename

* Convert all panel models.cue to thema

* Rewrite pluggen to use Thema

* Remove pkg/schema, and trim command

* Remove schemaloader service and usages

Will be replaced by coremodel-centric hydrate/dehydrate system Soon™.

* Remove schemaloader from wire

* Remove hangover field on histogram models.cue

* Fix lint errors, some vestiges of trim service

* Remove unused cuetsify cli command

public/app/plugins/panel/histogram/models.cue

@@ -14,23 +14,28 @@
 
 package grafanaschema
 
-import ui "github.com/grafana/grafana/packages/grafana-schema/src/schema"
+import (
+	"github.com/grafana/thema"
+	ui "github.com/grafana/grafana/packages/grafana-schema/src/schema"
+)
 
-Panel: {
-    lineages: [
-        [
-            {
-                PanelOptions: {
-                    ui.OptionsWithLegend
-                    ui.OptionsWithTooltip
-                    bucketSize?: int
-                    bucketOffset: int | *0
-                    combine?: bool
-                } @cuetsy(kind="interface")
+Panel: thema.#Lineage & {
+	name: "histogram"
+	seqs: [
+		{
+			schemas: [
+				{
+					PanelOptions: {
+						ui.OptionsWithLegend
+						ui.OptionsWithTooltip
+						bucketSize?:  int
+						bucketOffset: int | *0
+						combine?:     bool
+					} @cuetsy(kind="interface")
 
-                PanelFieldConfig: ui.GraphFieldConfig & {} @cuetsy(kind="interface")
-            }
-        ]
-    ]
-    migrations: []
+					PanelFieldConfig: ui.GraphFieldConfig & {} @cuetsy(kind="interface")
+				},
+			]
+		},
+	]
 }