Reproducible MDF content in HltSelRep

Ensures strict reproducibility of MDFs. It has no observable effect except for helping the testing in Moore.

• Initialize padding bytes in HltSelRep event model
• Reset packed data checksums on every event (much more useful for testing with streaming).
• Add a script to dump the bytes of the raw events, decompressing the DstData bank as needed.

Propagated from MR !1032 (merged) in 2018-patches

• [2018-04-06 00:13] Validation started with lhcb-gaudi-head-py3#115
• [2018-04-06 00:13] Validation started with lhcb-head#1810
• [2018-04-06 00:14] Validation started with lhcb-clang-test#912
• [2018-04-06 00:19] Validation started with lhcb-gaudi-head#1824
• [2018-04-06 00:26] Validation started with lhcb-tdr-test#111

changed title from {-Propagate MR !1032 (merged) from 2018-patches to master-} to Reproducible MDF content

changed the description

merged

mentioned in commit 28825968

changed title from Reproducible MDF content to Reproducible MDF content in HltSelRep