pg_checksum: add test for coverage

When Who What
2022-10-12 05:36:38 Michael Paquier (michael-kun) Closed in commitfest 2022-09 with status: Returned with feedback
2022-08-29 11:47:48 Daniel Gustafsson (d_gustafsson) Changed topic to Testing
2022-08-29 11:46:55 Daniel Gustafsson (d_gustafsson) Added d_gustafsson as reviewer
2022-08-29 11:46:52 Daniel Gustafsson (d_gustafsson) New status: Waiting on Author
2022-08-29 11:28:59 DongWook Lee (dongwooklee) Changed authors to DongWook Lee (dongwooklee)
2022-08-29 11:28:46 DongWook Lee (dongwooklee) Attached mail thread CAAcByaLPAK1e-Mpa5WUBATQsvXdiP5FXNX6+yqTrFZxg0vpngw@mail.gmail.com
2022-08-29 11:28:46 DongWook Lee (dongwooklee) Created patch record