x/auth: Get accounts 1 by 1

[ValarDragon]

In auth we currently do the state read for all accounts, and then verify signatures one by one, stopping at the first failed signature. This is sub-optimal, as the first signature may be invalid but we've done the IO for all the other accounts. We should instead get the accounts one by one, and then verify its signature. This is important to do since this account checking logic can get spammed via CheckTx.

This should end up not being a honest-case significant performance hit as we don't gain much speed by batching those I/O operations. (IAVL isn't doing a batch read, and the relevant memory pages won't leave RAM under decent RAM assumptions. This will hurt instruction caching, but I think its worth it given that each of these I/O reads are independent and saving one I/O read far outweighs time lossed due to instruction cache misses. )

[alexanderbez]

This is the context of the ante handler I take it?

[ValarDragon]

Yes

[alessio]

func getSignerAccs(ctx sdk.Context, am AccountKeeper, addrs []sdk.AccAddress) (accs []Account, res sdk.Result) {
	accs = make([]Account, len(addrs))
	for i := 0; i < len(accs); i++ {
		accs[i] = am.GetAccount(ctx, addrs[i])
		if accs[i] == nil {
			return nil, sdk.ErrUnknownAddress(addrs[i].String()).Result()
		}
	}

	return
}