* Make validate-schema CLI command work vs. disk
Previously, `grafana-cli cue validate-schema` would only validate the
CUE files that had been included at compile time. Now, the command
requires passing a grafana checkout root path, and will actually check
against live files on disk.
* Exempt validateScuemata from sec linter
* Nit: validateScuemata is a simpler, better name
* Try to fix validate-scuemata build step