Add thousand separator in token formatter

[ruuda]

In the anchor-integration branch we improve the impl_token! macro so it works for an arbitrary number of decimals, but it still prints amounts as ddddddd.ddddddddd, which is a lot better than printing the number of lamports, but we could still do better by printing it something like d,ddd,ddd.ddd_ddd_ddd.

Once we have this, it would be nice to use it for printing wLDO amounts in the multisig utility.