fix: add OCPP 2.0 DataTransfer outgoing support and B03 boot retry in Rejected state

fix: add OCPP 2.0 DataTransfer outgoing support and B03 boot retry in Rejected state

Add DATA_TRANSFER to OCPP20RequestCommand enum, buildRequestPayload
passthrough, schema registration, and response handler (P02.FR.02).

Allow BootNotification retry when station is in Rejected state by
adding inRejectedState() to the internalSendMessage gate (B03.FR.06).

Fix mock server: use OCPPCommCtrlr component for HeartbeatInterval
in SetVariables, add customerIdentifier in CustomerInformation.

Add unit tests for promiseWithTimeout and DataTransfer outgoing.