Dampen some useless commands

[MikeBishop]

This targets the two useless commands I identified in #591; if others are noted, I can add them. It's based on #571, since it needs some of the additional state that was picked up there; I'll retarget to main once that's merged.

• When charging stops (as reported by the TWC), stopAskingToStartCharging is set on the last-connected vehicle if that vehicle last reported an estimated time-to-completion of less than five minutes.
• Before sending a start-charge command, the vehicle's last-reported charge status is checked. No start/stop command is sent if the vehicle reported being disconnected or done charging, and no charge command is sent if the vehicle reported that it was already charging.

It now also eliminates an additional useless command I discovered from my tesla-proxy logs:

• If the charge limit is being set to the same limit the car already reports, no charge limit command is sent.

[ngardiner]

Hi @MikeBishop, I think this would be a good candidate for merging prior to Feb 1 to reduce potential API costs, but I see that the PR targets the mqtt_data branch, is that intentional & do you think it's a good time to merge?

[MikeBishop]

That was deliberate, because it builds on things contained in that branch but I wanted this to be reviewable separately. I think both are ready to merge; we can retarget this to main once #571 is in.