fix: Order upgrades by block height rather than name to prevent panic

[derekadams]

Description

Closes: cosmos#11707

The existing "last upgrade check" functionality orders upgrades based on name in descending order when locating the most recent upgrade. This fails for named upgrades and many other scenarios. Order by upgrade block height descending in order to properly find the most recent upgrade.

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[iramiller]

seems like a pretty reasonable change... the overall approach of doing this work on every begin block feels misguided, but for now at least this fix will make it work correctly.