Add extra shared import functions - attempt to unblock regression fixes dependent on 23689 (fixes participant import)

[eileenmcnaughton]

This is an attempt to get away from fixing known breakage
being blocked by
#23689

These functions should be mostly as-yet-unused, or only minorly changed
but required to fix the known issues

@totten - I don't know tht this will fix the activity import breakage but it should unblock me fixing it rather than keeping waiting on #23689 & I can easily rebase that over this if merged

[civibot]

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[eileenmcnaughton]

This fixes Participant import - so there is one import fixed with this - at this stage activity is the same amount broken with or without but this helps with the tools to fix activity