tests

Add Postgre function: `DATE_TRUNC` #2232

Job	Run time
Build `sea-query`	36s
Build `sea-query-binder` (async-std, rustls)	49s
Clippy	38s
Rustfmt	20s
Build `sea-query-postgres`	37s
Build `sea-query-rusqlite`	31s
Unit Test	1s
Derive Tests	1s
SQLite	1s
MySQL	1s
MariaDB	1s
Any	1s
PostgreSQL	1s
	3m 38s

Provide feedback