fix: use OCPP version-specific parameter keys for meter value measurands

fix: use OCPP version-specific parameter keys for meter value measurands

Remap keba-ocpp2 template configuration keys from OCPP 1.6 names to
OCPP 2.0 variable names (MeterValuesSampledData → TxUpdatedMeasurands,
MeterValueSampleInterval → TxUpdatedInterval, AuthorizeRemoteTxRequests
→ AuthorizeRemoteStart). Remove OCPP 1.6-only keys with no 2.0
equivalent. Use StandardParametersKey union to resolve the correct
key at runtime based on OCPP version.