[ATR-19997] Propagate Filter output collections in RDOtoRDOTrigger. Tidy up feature access.

Working towards fixing the crash reported here https://its.cern.ch/jira/browse/ATR-19997?focusedCommentId=2778617&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-2778617

Compliance fixes to the InputMakers

• We should not be re-attaching existing "muons" link. It can be fetched from the parent ("seed") Decision object. cc @sshaw
• We should not be re-attaching existing jet link as "feature". It can be fetched from the parent ("seed") Decision object. Also - only HypoAlgs should attach links with the name "feature". (If this turns out to be really needed, then the name of the link should change.)
• We should use TrigCompositeUtils::viewString() instead of "view" to minimise hard-coded strings.

This causes TrigBjetBtagHypoAlgMT.cxx to fail online validation, the presence of a "feature" link in the InputMaker's output tricked the validation into thinking that TrigBjetBtagHypoAlgMT.cxx was acting like a combi-hypo

• Add dummy "feature" link in TrigBjetBtagHypoAlgMT.cxx, until a real feature is ready. cc @cvarni

I found that Filter navigation collections were not being propagated to the output file. collectHypos and collectFilters were being given a sequencer which was one level too high, but collectHypos had a slightly different logic and was able to cope. Hence some output was generated and I did not spot before.

• Collect all hypos and filters from AthSequencer("HLTAllSteps") - BUGFIX
• Add extra protection in TrigCompositeUtils::getRejectedDecisionNodes to not follow invalid seed links. Prints warning that navigation information is incomplete in the file.

This then caused Tau monitoring to crash as we started to find tau features - but return invalid element links. This I believe is understood and will be fixed by @carquin as discussed on mattermost (it's the Py:TriggerConfig WARNING The producer of the TAUCaloRoIs not in the menu, it's outputs won't ever make it out of the HLT issue)

• Make invalid online taus print a WARNING and then continue