Can't deploy multiple Airflows using k8s executors into same namespace

Noticed this on a customer setup.
The bug is pretty simple: We always use the same name for the executor Pod template ConfigMap. In case you have multiple Airflows, the two "fight" over writing to that ConfigMap. This results in a reconciliation battle ⚔️ There are only loosers...

Instead the CM should be called something like `<stacklet>-executor-pod-template`