Stop Balances pallet erroneously double incrementing and decrementing consumers

[liamaharon]

Closes #1970

Follow up issue to tackle, once the erroneous double incrementing/decrementing has stopped: #2037

[kianenigma]

Perhaps we could write a script that scrapes extrinsics for for accounts that had their consumers erroneously incremented and generates a migration to decrement them?

First glance, this will be a race that you're alway behind, as more accounts can get their consumers incremented by mistake in the timespan while we wait for the migration to execute.

[bkchr]

We should first deploy the fix and then let the fix come in a later runtime upgrade.

[liamaharon]

We should first deploy the fix and then let the fix come in a later runtime upgrade.

I agree, created a seperate issue for the fix #2037.

So, this PR is ready for review and we should not unnecessarily delay merging it to reduce the total number of broken consumers.

[ggwpez]

What to do with chains that got fucked by this before the fix applied?
eg https://substrate.stackexchange.com/questions/11166

[liamaharon]

What to do with chains that got fucked by this before the fix applied? eg https://substrate.stackexchange.com/questions/11166

Need to retroactively fix it #2037

[ggwpez]

Prepared this to see what needs fixing. Note that #1976 is not yet on Polkadot master, as it is on 1.4 - not 1.3.