The traits to plug new engines became more clear. It would help us
while implementing the picodata engine.

tarantool uses async replication by default, and it is possible to try selecting from a replica that does not have the space or the data yet, which can cause flaky tests
now, we configure storage replicaset and enable sync replication for spaces to work with
Closes #369

Previosly we had a very complicated logic for INSERT operator:
we always generated a motion node under INSERT and generated
bucket_id with a special motion command in this virtual table.
As a side effect we made motions even for those INSERTs that was
possible to execute locally.

Another problem was caused by the column type derivation in
INSERT .. VALUES .. expressions. If any column in the first row
contained NULL it confuses Tarantool and it returns scalar (or
even boolean!) type instead. And there is no projection type cast
in Tarantool's insertion. As a result we often had type mismatch
errors in INSERT .. VALUES .. queries.

The solution is to rewrite this weird logic from the scratch.
Now we rewrite the tree somehow like this:

insert into t1 (a, b) values (1, 2)

=>

insert into t1 (a, b, bucket_id)
select
  COL_1,
  COL_2,
  bucket_id(
    coalesce(cast(COL_2 as string), '')
    || coalesce(cast(COL_1 as string), '')
  )
from (
  select
    cast(COLUMN_1 as integer) as COL_1,
    cast(COLUMN_2 as unsigned) as COL_2
  from (values (1, 2))
)

- added count, sum aggregates, which can be used in queries with group by

currently we mean expression with arithmetic, bool and
unary operations by arbitrary expr

deploy: remove shell tag from deploy-luarocks job to run commands inside sbroad-builder instead of runner shell envrironment

Distribution setter is one of the most confusing and wired parts
of the code. One day I'll rewrite it in a more clear way (but not
today, sorry). But here is a small refactoring to make the parent
to child column mapping logic more clear in the code.

previously we suggested that operand of arithmetic expression is column.
it allows use alias (a as a1 + b as b2). ofcourse operand must be value
(a), while alias usage must be available for expression (a + b as sum)

we need to support arbitrary expressions consisting of logical, comparison and arithmetic operations and as sub-expression of aggregates. previously we added arithmetic exprs to selection ans join. this commit supports arithmetic (and only arithmetic) as a part of projection