This commit modifies the k8s operator to allow for customisation of the ingress class name
via a new `OPERATOR_INGRESS_CLASS_NAME` environment variable. For backwards compatibility,
this defaults to `tailscale`.
When using helm, a new `ingress.name` value is provided that will set this environment variable
and modify the name of the deployed `IngressClass` resource.
Fixes https://github.com/tailscale/tailscale/issues/16248
Signed-off-by: David Bond <davidsbond93@gmail.com>