Thanks to the updates in tarantool module we don't use tarantool
symbols to work with decimal. As a bonus we can remove our mocking
framework with dynamic linking of the decNumber library to cargo
test binary.

Now coordinator dispatches SQL patterns with separated parameters.
It would help us to cache patterns on the segments as prepared
statements one day and skip SQL parsing.

Also we have faced a Tarantool bug

https://github.com/tarantool/tarantool/issues/7283

and made a hot fix in the Picodata fork. As a result we have also
migrated sbroad CI to our fork.

We migrate from the `decimal` crate (used decQuad from decNumber
to store the numbers) to Tarantool internal types provided by the
Rust module. The reason was to make IR numeric values easy
serializable to the query parameters (a part of the executor
refactoring).

The problem with Tarantool internal types is that the internal
decNumber representation is provided by Tarantool ABI. So we always
need Tarantool itself to use the types. It is ok for integration
tests, but for unit tests with `cargo test` it is a problem. As a
solution we have implemented some mocking infrastructure to build
a static library based on the Tarantool decNumber, MsgPuck and some
wrappers over them both to make unit tests work.