Remove CoreState.starting

[balloob]

Followup to #6189. Should not go into 0.39.

Hass has an enum for states. One of them is CoreState.starting. However, due to the way the system is setup, we will never be in this state and neither do we have any code that depends on it.

[mention-bot]

@balloob, thanks for your PR! By analyzing the history of the files in this pull request, we identified @kellerza, @fabaff and @pvizeli to be potential reviewers.

[balloob]

No need to clear the cache if cache is just an empty dict

[balloob]

Enforce that when we're running, we don't restore.

[balloob]

All paths ensure _load_restore_cache is set.

[pvizeli]

I like this state and it can sugestion that we are in bootstrap. I think we can use that also in future. Why we not use starting on HomeAssistant.init and after call hass.start in is in state running (like it is)? So we know that the start is not calling jet and we stay inside bootstrap process.

[balloob]

@pvizeli in that case we should also change not_running to stopped. In that case we start with starting (or maybe rename it init):

• init
• running
• stopping
• stopped

[pvizeli]

👍 realy greate idea. Since we are async everey state is finally and can not revert. So we loop over this state flow and know where we stay inside processs. I'm allready thinking to future for splitung up into multiproccesing.