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

scripts/drone/steps/lib.star

@@ -1149,36 +1149,6 @@ def get_windows_steps(edition, ver_mode):
 
     return steps
 
-
-def validate_scuemata_step():
-    return {
-        'name': 'validate-scuemata',
-        'image': build_image,
-        'depends_on': [
-            'build-backend',
-        ],
-        'commands': [
-            './bin/linux-amd64/grafana-cli cue validate-schema --grafana-root .',
-        ],
-    }
-
-
-def ensure_cuetsified_step():
-    return {
-        'name': 'ensure-cuetsified',
-        'image': build_image,
-        'depends_on': [
-            'validate-scuemata',
-        ],
-        'commands': [
-            '# It is required that the generated Typescript be in sync with the input CUE files.',
-            '# To enforce this, the following command will attempt to generate Typescript from all',
-            '# appropriate .cue files, then compare with the corresponding (*.gen.ts) file the generated',
-            '# code would have been written to. It exits 1 if any diffs are found.',
-            './bin/linux-amd64/grafana-cli cue gen-ts --grafana-root . --diff',
-        ],
-    }
-
 def verify_gen_cue_step():
     return {
         'name': 'verify-gen-cue',