feat: implement datetime type and to_date function

Cargo.lock

doc/sql/query.ebnf

sbroad-cartridge/cartridge/roles/sbroad-storage.lua

sbroad-cartridge/src/cartridge/config.rs

sbroad-cartridge/src/init.lua

sbroad-cartridge/src/utils.rs

sbroad-cartridge/test_app/test/data/config.yml

sbroad-cartridge/test_app/test/integration/api_test.lua

sbroad-core/src/backend/sql/ir/tests/selection.rs

sbroad-core/src/builtins.lua

sbroad-core/src/cbo/selectivity.rs

sbroad-core/src/core-storage.lua

sbroad-core/src/executor/engine.rs

sbroad-core/src/executor/engine/mock.rs

sbroad-core/src/executor/protocol.rs

sbroad-core/src/executor/result.rs

sbroad-core/src/executor/tests/exec_plan.rs

sbroad-core/src/frontend/sql.rs

sbroad-core/src/frontend/sql/ir/tests.rs

sbroad-core/src/frontend/sql/query.pest