Adds a new flag (on by default) that enables generating a TLS
certificate and sending it to ironic via heartbeat. Whether
ironic supports auto-generated certificates is determined by
checking its API version.
Change-Id: I01f83dd04cfec2adc9e2a6b9c531391773ed36e5
Depends-On: https://review.opendev.org/747136
Depends-On: https://review.opendev.org/749975
Story: #2007214
Task: #40604