TrigDecision+HLTResult: decode ROB truncation status
Decode the per-ROB truncation status and store it in the TrigDecision
.
Since we only support one truncation status, we use the convention of
reflecting the main HLT Result ROB if available, otherwise the combined
status of all other ROBs (but there should only be one for a given
non-Physics stream).
In any case, for severe truncations (debug stream) the status from the event header has priority.
None of this code will actually be used until will mark some of our EDM collection as "truncatable". This will follow as a separate MR.
Companion to !64583 (merged) and relates to ATR-27986. cc @tamartin