x/auth InitGenesis changes account numbers if there's a skipped entry.

[SpicyLemon]

Summary of Bug

In the x/auth InitGenesis function, if the provided GenesisState.Accounts has a max AccountNumber that is greater than the number of Accounts, the account numbers of the created accounts are different from those provided.

For example, if GenesisState.Accounts has account numbers 0, 1, 3, 4, 5; then InitGenesis will change 3, 4, and 5 to 2, 3, and 4 (respectively).

Version

First noticed in 0.46.0, but it looks like it's always been this way.
Still exists in main as of commit 6af89d6ce3f43e8a67ea2ee93c5a49e395ebd09d Wed Aug 24 23:13:11 2022 +0200.

Steps to Reproduce

1. Create an x/auth GenesisState with a single Accounts entry that has account number 10.
2. Call InitGenesis.
3. Look up the account.

Expected result:
The account has account number 10.

Actual result:
The account has account number 0.

The reason I found this, though was in Provenance's import/export sim. Our sim created several accounts, and removed one. Then it exported the current state and imported it again (as a separate app). Then it compared the state of the two apps and found that the states were different because the 2nd app had reduced account numbers.

[SpicyLemon]

I fixed this in our fork with this PR: provenance-io#228
That PR also contains the fix for #13028, but the rest is just for this.

That solution still fixes entries with duplicated account numbers (e.g. if they're all '0'), but only changes them when they're duplicates. It also updates the global account number to the largest one, so new accounts will go up from there.

[ValarDragon]

Any chance this PR can be upstreamed to mainline SDK? This feels like a notable problem to me.

cc @julienrbrt

[julienrbrt]

Thanks for the ping. I'll have a look 👍🏾