Make EVSE mockable and add mock

[christopher-davis-afs]

Describe your changes

This set of changes makes EVSE derived from an interface similar to what we did with ComponentStateManager,
and adds a mock to our set of mocks for v201.

Checklist before requesting a review

• I have performed a self-review of my code
• I have made corresponding changes to the documentation
• I read the contribution documentation and made sure that my changes meet its requirements

[christopher-davis-afs]

CC: @shankari

[Pietfried]

It looks like after a rebase you need to also update

std::map<int32_t, std::unique_ptr<Evse>>& evses;
and
explicit SmartChargingHandler(std::map<int32_t, std::unique_ptr<Evse>>& evses);.

and change the the EvseInterface type

Except for me this looks good!

[christopher-davis-afs]

It looks like after a rebase you need to also update

std::map<int32_t, std::unique_ptr<Evse>>& evses; and explicit SmartChargingHandler(std::map<int32_t, std::unique_ptr<Evse>>& evses);.

and change the the EvseInterface type

Except for me this looks good!

Updated :)

[Pietfried]

👍

[drmrd]

Contributes to #361