Update to support Datalog version 3.3.

[preuss-adam]

Submitting on behalf of @saoirse-a

Adds support for Datalog features from Biscuit 3.3 except for FFI, which are:

1. Syntax change: sets use braces not brackets
2. Syntax change: Strict equality uses === and !==
3. Syntax change: || and && compile to LazyAnd / LazyOr
4. Reject if checks
5. Null terms
6. Array terms
7. Map terms
8. Closure operators
9. Op: Heterogeneous equality / nonequality
10. Op: Lazy and/or
11. Op: TypeOf
12. Op: Get
13. Op: Any
14. Op: All
15. Op: TryOr

Refactors

Op.Value and Expression.Value are eliminated, instead Term inherits from Op and Expression, saving an indirection/allocation.

SchemaVersion refactored (and duplicate implementation of SchemaVersion eliminated) to be clearer and avoid an unnecessary allocation.

Test changes

SamplesTest changed to deal with the additional complexities that maps bring. Most importantly, we cannot rely on a byte-for-byte comparison of the generated datalog block with the sample, because maps do not have a canonical order among their members. Instead we rely on the serialise / deserialise step to check roundtrips and add a check that we are generated the same version number for blocks (which is the only other thing I saw caught by these assertions).