codegen: Refactor core jennies for reusability, add version-picking metajennies (#58995)

* Add each-major jenny, refactor TS jenny for it

* Introduce LatestJenny, refactor GoTypesJenny for it

pkg/codegen/tmpl/gen_header.tmpl

@@ -0,0 +1,11 @@
+// THIS FILE IS GENERATED. EDITING IS FUTILE.
+//
+// Generated by:
+//     {{ .MainGenerator }}
+// Using jennies:
+{{- range .Using }}
+//     {{ .JennyName }}
+{{- end }}
+//
+// Run 'make gen-cue' from repository root to regenerate.
+