Making order number generator issues more visible to stores

[RyanofWoods]

When an Order number is generated, if a collision occurs, it will check how many orders there are in the database. If over half of the possible number possibilities are already taken, then the order length is temporarily increased by 1 to avoid collisions.
https://github.com/solidusio/solidus/blob/main/core/app/models/spree/order/number_generator.rb#L38

This isn't optimal as counting the order records where there are millions takes multiple seconds. This used to be worse problem before as we would calculate the order count for each collision, until I fixed it:
#4722

Looking at the bigger picture, this solution hides the problem from stores and puts performance cost on the user. We are also assuming that stores are okay with their order length being changed. What if they have integrations not expecting this?

I am wondering whether we should just have an health check instead for this (could be on the admin), and remove the counting logic from the generator. If we do this, we could add the health check first, and put the generator count logic behind a config, so that stores have a chance to check their generator health before changing generator logic.

WDYT?