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

embed.go

@@ -4,13 +4,7 @@ import (
 	"embed"
 )
 
-// CoreSchema embeds all core CUE files, which live in packages/grafana-schema/src
+// CueSchemaFS embeds all schema-related CUE files in the Grafana project.
 //
-//go:embed cue.mod cue packages/grafana-schema/src/schema/*.cue packages/grafana-schema/src/scuemata/*/*.cue packages/grafana-schema/src/scuemata/*/*/*.cue
-var CoreSchema embed.FS
-
-// PluginSchema embeds all expected plugin CUE files and plugin metadata from
-// within the public/app/plugins subdirectory.
-//
-//go:embed public/app/plugins/*/*/*.cue public/app/plugins/*/*/plugin.json
-var PluginSchema embed.FS
+//go:embed cue.mod packages/grafana-schema/src/schema/*.cue public/app/plugins/*/*/*.cue public/app/plugins/*/*/plugin.json
+var CueSchemaFS embed.FS