sql: invalid integer type in arithmetic operations

Tarantool SQL used to return 'number' type in request metadata
for arithmetic operations even when only 'integer's were used.

This also fixes query planner optimisation bug:
SELECT a FROM t1 WHERE a+0 IN (SELECT a FROM t1);
used to open a new ephemeral table with OpenTEphemeral when
it is not required (introduced by 2b22b913).

Closes #4103