pre-genesis messages tidy-up

Add a new function pretime_message() to avoid bespoke printf in the start up sections of code. Stops silly things like adding a time field to the output before time is created for the odd few messages that use message(). Also add some consist flushes to all these messages so that they stand a better chance of being delivered when an MPI takedown is in progress (that can be very confusing and look like a crash). Finally make sure that the greeting is delivered ahead of any other messages from other ranks so that they do not interleave. Only really an issue when being verbose.

Note based on !1707 (merged) as these changes are also for that, so that should be merged first.

added MPI cleanup code health enhancement labels

requested review from @matthieu

assigned to @pdraper

Messing about with !1707 (merged) kept getting messages in a messy order so started looking at why and came up with all this. No urgency and feel free to decline...

changed the description

added 2 commits

• 28ba4420 - Accept --interleave and warning about deprecation
• b0aaeb0a - Merge branch 'interleave-as-default' into pretime-messages

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added 1 commit

• dee10e11 - Formatting

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marked this merge request as ready

added 14 commits

• dee10e11...529d72fb - 13 commits from branch master
• 8aff5671 - Merge branch 'master' into 'pretime-messages'

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added 2 commits

• b09c9d7a - Use the pre-genesis messaging mechanism also in the stand-alone FOF code
• b71bc8ac - Make the new messages related to interleaving options alos use the new mechanism

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approved this merge request

merged

mentioned in commit ec7cd083