The commit adds validator sources uses combination of local files and
vector-store's files. In `build-env` there are definition of vector-store git
repository and revision on which validator will be built. `cargo-toml-template`
is script for printing current `Cargo.toml` to the stdout. After updating
`build-env` developer needs to update new configuration with
`./cargo-toml-template > Cargo.toml`. Git revision is used in several places in
`Cargo.toml` and will be used for building `vector-store`, so for better
handling git revision it should be setup only in one place.
The validator is divided into several crates to be able to built it within
scylladb and vector-store repositories. Here we need to create a new validator
crate with simple `main` function and call `validator_engine::main` there. We
provide tests written in scylladb repo in `validator-scylla` crate. The commit
provides empty `cql` test case, which should be filled in the future.
