Support for closures

[divarvel]

The goal of this branch is to explore how to add support for closures in the stack machine

• closures are represented as a list of ops and a list of parameter names

• closure parameters can be used like variables

• variable names must be unique, so shadowing is forbidden

• boolean operators use laziness and push the rhs closure on the ops list only if needed (without recursion)

• .any() and .all() use recursion to compute results

• [x] closure support in datalog::expression::Op

• [x] closure support in format::schema

• [x] closure support in parser

• [x] closures for lazy boolean operators

• [x] closures for .any() and .all()

• [ ] prevent shadowing in closure arguments (parser, deserialization, execution?)