TWC/Tesla: use charger api.PhaseCurrents over vehicle api.CurrentGetter

[andig]

In case of TWC/Tesla, we're expiring the rate limit due to #14226 when charging below 6A since Tesla needs validation if limit really is applied on vehicle (most likely, that's a vehicle bug). For this purpose, api.CurrentGetter has been added on Tesla and is relayed by TWC to the vehicle if connected.

With #14622, instead of using charger's api.CurrentGetter (which relays to vehicle's api.CurrentGetter in case of TWC) we can resort to charger's api.PhaseCurrents to determine charging above limit as fallback. This PR ensures that the fallback is used by removing the Tesla's api.CurrentGetter and ensuring that charger's api.PhaseCurrents is invoked on api.ErrNotAvailable returned by TWC.

Supports #14616

[andig]

Published Docker tesla.

[GrimmiMeloni]

Apart from the comment nitpick, this looks good to me.

[andig]

@FraBoCH hattest Du eine Chance, das auszuprobieren?

[FraBoCH]

Just tested the :tesla docker image. It works as expected with the following typical scenario:

• switch to mode now: start charging at 16A
• switch to min+ev: send charging amps to 1A but Tesla only going to 5A. Then evcc detected the issue. I got the warning Garage: charger logic error: current mismatch (got 5.1A measured, expected 1A)
• Evcc send once again charging amps to 1A and then Tesla complies
• Charging continue at 1A as expected.
  Looking forward to have it in production with the next release 👍🏻