Auctions are disabled for vaults with collateral over the auction limit

[alcueca]

Vaults with more collateral than the auction limit cannot be auctioned.

        limits_.sum += balances_.ink;
        require (limits_.sum <= limits_.line * (10 ** limits_.dec), "Collateral limit reached");

One solution is to revert the order of the two lines above, so that the limit on auctions is not a hard limit. Instead, the limit could be breached, but once it's breached no further auctions can proceed until it gets below the line again.

Alternatively, we can have the Ladle check the auction limits before allowing to post collateral, but that's messy.

Discuss.

[alcueca]

Disabled in governance proposals (Arbitrum, Mainnet). To be fixed in the Witch refactor.