Ensure ESPHome dashboard connection recovers if its down when core starts

[bdraco]

Proposed change

If the dashboard was down (or not started yet) at startup, we would not try again later to connect until core was restarted.

fixes #96447

Unfortunately it means we end up reloading all the entries when it does come back online later but thats still better than being offline forever. Ideally supervisor would start the dashboard before core so this condition doesn't ever happen but that is outside the scope of core.

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[home-assistant]

Hey there @OttoWinter, @jesserockz, mind taking a look at this pull request as it has been labeled with an integration (esphome) you are listed as a code owner for? Thanks!

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[bdraco]

Need to test this on production as well but can’t take my dashboard down right now

[bdraco]

This fixes it, but it's also confusing if the dashboard doesn't know about the device it reports as unavailable instead of unknown. That's a different problem though for another pr #96455

[bdraco]

thanks