Update inithook services

[JedMeister]

Built on top of #66

Note: deeper testing is required before merging this commit. See TODO notes below.

This PR provides a new approach to management of getty1 (ff4cbbd):

• (re)implements an inithooks.service:
  • starts after relevant getty1 service at boot
  • conflicts with getty1 services so will kill any existing getty1 service/s
  • when initihooks.service (running either inithooks or confconsole) exits, a new inithooks-restart-getty.service is started - regardless whether inithooks/confconsole exits cleanly or not
  • new inithooks-restart-getty.service runs a script which waits for inithooks.service to be stopped and then starts the appropriate getty1 service

TODO:

• buildtasks updates
  • multiple inithook legacy service files still exist as overlays in buildtasks! ideally these should be removed and included within the inithooks package (with relevant conditional requirements). It is probably possible to consolidate them into 2 services; once for bare metal and VMs, and another for containers.
• Testing:
  • basic initial testing shows that it works as intended; however there have been some minor tweaks since testing
  • has not been tested on repeated boots
  • has only been tested in a KVM VM - needs testing on a container