Refactor: Use last ambientTemperature from lastState

[danielfeismann]

this should build upon #853

within ThermalGrid.energyDemand I introduced the last ambientTemperature very quick and dirty. This can and should be refactored. The ambientTemperature of the last state is also part of the last HpState and can be taken from there. That would make the method more comprehensive. This may lead to further adaptions...

see:

          Note from my side: In my opinion both temperatures are necessary here, the ambientTemperature of the last state and the actual one. Since the HpState contains the lastAmbientTemperature this can be done nicer and would be a good HiWi-Job. As well some tests for different cases like falling and rising temperature would be great.

Originally posted by @danielfeismann in #853 (comment)

[danielfeismann]

Blocked by #929

Note to self: After #929 is completed update this issue here