That bit is unlogged and therefore it's wrong to consider it in WAL page
comparison.

Add a test that tickles the case, as branch testing technology allows.

This has been a problem ever since wal consistency checking was
introduced (commit a507b869 for pg10), so backpatch to all supported
branches.

Author: 王海洋 (Haiyang Wang) <wanghaiyang.001@bytedance.com>
Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://postgr.es/m/CACciXAD2UvLMOhc4jX9VvOKt7DtYLr3OYRBhvOZ-jRxtzc_7Jg@mail.gmail.com
Discussion: https://postgr.es/m/CACciXADOfErX9Bx0nzE_SkdfXr6Bbpo5R=v_B6MUTEYW4ya+cg@mail.gmail.com