refactor(ocpp): remove static alias forwarding from OCPPServiceUtils class

refactor(ocpp): remove static alias forwarding from OCPPServiceUtils class

Replace OCPPServiceUtils static property aliases with direct function
imports. All 7 aliases (buildTransactionEndMeterValue, mapStopReasonToOCPP20,
restoreConnectorStatus, sendAndSetConnectorStatus, stopRunningTransactions,
buildSampledValue, getSampledValueTemplate) were trivial forwarding to
standalone functions already defined in the same file.

Consumers now import these functions directly, reducing indirection and
moving toward dissolving the extraneous utility class.