operation: Make `loki-mixin` available to non-jsonnet users as well.

Currently Loki operators who are using jsonnet can only benefit from dashboards and alerts from [loki-mixin](https://github.com/grafana/loki/tree/main/production/loki-mixin). We should support those dashboards and alerts for non jsonnet users as well.

Something similar to what mimir does with [mimir-mixin-compiled.](https://github.com/grafana/mimir/tree/main/operations/mimir-mixin-compiled)
