Also fix some documetation style

Also make a "add_bool" test fixup

We need this refactoring to move all node plan methodes to the new
Nodes structure. Otherwise we have to put a mutable lock for the
whole plan structure rather then on the nodes list. It makes
porblems with API refactoring otherwise.

Also move this Plan implementation method to expressions.

Also "set_distribution()" function is a Plan method now.

BREAKING CHANGE: move from branch-based references in the tuple to
the array-based. Also add a logical ID to all relational nodes and
keep it in all its child tuples.

Now, our reference coordination system in a tuple looks like:
- parent relational node logical ID (we don't know actual position
  in the nodes list, so use "secondary index")
- target - i.e. a position of the reffered node in the relational
  node's children list
- posirtion in the reffered relational child node output tuple

Previously distribution was calculated in the node constructor. It
is a wrong design as the tree would be transformed multiple times
and there is no reason to recalculate distribution on each step.
We need distribution only on the last transformation when we insert
Motion nodes. So, this refactoring makes tuple distribution optional
and moves distribution logic to a separate function 'set_distribution()'.

feat: migrate getting vshard count of buckets from lua to rust and added tarantool logging to proxy functions

Was fixed interaction format between lua and sbroad rust lib. In current implementation sbroad encodes query result to yaml and send it to lua app. Lua app gives yaml and decodes it to lua table. After apply this changes lua app will receive lua table and yaml transformations will not be needed.

We need it to serialize IR to SQL correctly - otherwise we'll lose
information about subquery name. Not good.

Migration to tarantool module master branch for more conformable working
with Lua calls.

Move this logic to a separate function and add one more test.

Previously,  unit tests and code lived in the same '*.rs' file.
We have written too much tests and these files became bloated
(up to 1000 lines) - it is difficult to navigate them. So, lets
make a refactoring.

Now we can build it with cargo doc.

We expect that every relational node contains a reference to the
row expression node, that contains only aliases (expressions with
names). We need this convention to simplify SQL -> IR transformation.

Previously we had an alias only for reference, that was strange and
incorrect. Now we can add an alias name to any expression in the
tuple.