Adopt Tx prioritization

[liamsi]

Summary

With upgrading the SDK to 0.46.x (beta is tagged) and tendermint 0.35.x, we get Tx prioritization. But we should make sure that this also properly applies to messages/data in the same namespace. Or as @musalbas put it:

for validators I think we should introduce a tx prioritisation mechanism where if there are multiple transactions in the same namespace, the one that pays the highest fees gets included first
When ordering messages in the block
This is so that sovereign zk rollups can impose block size limits... Because generating proofs is expensive (edited)
So DoS resistance is needed

This is somewhat critical for launch and hence for incentivized testnet too. Let's add a test-case that asserts the above behaviour.

[evan-forbes]

closing as we updated to v0.46 of the sdk, but also created #513