Move placement policy parsers to SDK about neofs-node

[alexvanin]

We've moved JSON parsers of placement policy to the neofs-api-go in nspcc-dev/neofs-api-go#186 and nspcc-dev/neofs-api-go#189

JSON is a convenient way to represent placement policy in a non-binary way. JSON fields are specified in protobuf files in neofs-api. However Query Language isn't.

I am not sure QL grammar will be a part of specification. If it will be, then it makes sense to move it to neofs-api-go. Otherwise it would be better to put QL parser in separate repo with detailed description or keep it in neofs-node for a while.

[realloc]

SQL-like QL is part of neofs-cli and it was shown in our presentations many times. This should make external observer think it is NeoFS API integral part, though it's not described in neofs-api directly.

I suggest to have SQL-like QL implemented in neofs-api-go for convenience. Most probably we will add SQL-like QL grammar declarations in neofs-api later, when we agree on tools and format.

[realloc]

Should be reconsidered after separate neofs-client and neofs-sdk releases.

[roman-khimov]

I think we can move it now to neofs-sdk. It's used by S3 authmate code and at the moment this requires importing neofs-node. The package itself is rather small and doesn't have any dependencies on neofs-node code, so it can be moved easily.