store: write extensive tests that exorcize store/*

[odeke-em]

Summary

We need store/* at its best shape and to achieve that we need to exorcise all edges of it, finding what works, what conditions it trips under, how and when... When we finally have celestiaorg/smt as the store frontend it'll be very vital to ensure backend breakages don't occur silently but also to figure out how and what could be avoided. Almost similar to #10297

/cc @robert-zaremba @cuonglm in preparation for our Thursday meeting.

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[robert-zaremba]

We can use simplified version of #10297 (comment) to test if after:

• bunch of set / delete / we have the right data
• after commits and rollbacks we still have the right data

[tac0turtle]

closing as facu is working from a different issue on this