refactor(sbroad): Value::cast

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

sbroad/sbroad-core/src/executor/result.rs

sbroad/sbroad-core/src/executor/vtable.rs

sbroad/sbroad-core/src/ir/value.rs

sbroad/sbroad-core/src/ir/value/tests.rs

src/sql.rs