[Feature]: vAMM shapes count towards available volume for liquidation

[EVODelavega]

When the network attempts to dispose of its position as part of the liquidation strategy, vAMM shapes have to be included in the available volume on the book. When the network is configured to consume 10% of the available volume, and there's an available volume on the book of 50 + 50 through vAMM shapes, the network should place an order of size 10, as per spec:

https://github.com/vegaprotocol/specs/pull/2218/files#diff-3d81a39049a36bb18ecac5bd2f70835f6faabe4410a489eddc8f531411322bacR43

The liquidation engine must be able to call on the AMM engine to get the available volume at the given price point, and add it to the volume on book.