sql: cleanup usage of ToSql

Moved custom ToSql trait including Send + Sync from lib.rs to sql.rs.
Replaced most params! and paramsv! macro usage with tuples.

Replaced paramsv! and params_iterv! with params_slice!,
because there is no need to construct a vector.

src/test_utils.rs

@@ -425,7 +425,7 @@ impl TestContext {
         };
         self.ctx
             .sql
-            .execute("DELETE FROM smtp WHERE id=?;", paramsv![rowid])
+            .execute("DELETE FROM smtp WHERE id=?;", (rowid,))
             .await
             .expect("failed to remove job");
         update_msg_state(&self.ctx, msg_id, MessageState::OutDelivered)