[V124-specific] Emit EventTypeInactiveVault and EventTypeRetiringVault events appropriately (for future network versions only, rather than retroactively)

[V124-specific]

Intended to be possible code to close #1700
'Emit event on retired vault'.

If there's interest, I would be be very happy to make this a #check-lint-warning [Retroactive event changes] for historical consistency, though Midgard blockstore hashes would be affected.
(Like !3138 and !3038 (merged), I believe.)

I am also curious to know whether there is inclination to have explicit event emission upon vault migration being complete (namely when the number of RetiringVaults goes from non-zero to zero).