Refactor: split charger into current- and power controllers

[andig]

This PR is an investigation into splitting chargers into:

• CurrentController: typically wall boxes
• PowerController: typically heating devices, some chargers (ChargeX)
• no controller ability beyond on/off: switch sockets

TODO

• move all current control and phase switching logic from Loadpoint to core.currentController
• refactor switchSocket to declare required power and remove Controller interfaces
• think about refactoring ChargeState as part of Charger, potentially separate PR

Refs #6301, #7207

[maatinh]

Amperfied solar.connect kann auch mit Leistung statt Strom gesteuert werden und schaltet darüber auch selbstständig zwischen 1P/3P.

[DerAndereAndi]

Just a note: with EEBUS both variants should be possible in the same charger implementation as it depends on the chargers EEBUS version and implementation which is being supported. And it can also make sense to use currents e.g. for ISO connected cars and power for PWM.