Add checkpoint and redo LSN to LogCheckpointEnd log message

Hi,

It is useful (for debugging purposes) if the checkpoint end message
has the checkpoint LSN and REDO LSN [1]. It gives more context while
analyzing checkpoint-related issues. The pg_controldata gives the last
checkpoint LSN and REDO LSN, but having this info alongside the log
message helps analyze issues that happened previously, connect the
dots and identify the root cause.

Attaching a small patch herewith. Thoughts?

[1]
2021-12-23 14:58:54.694 UTC [1965649] LOG: checkpoint starting:
shutdown immediate
2021-12-23 14:58:54.714 UTC [1965649] LOG: checkpoint complete: wrote
0 buffers (0.0%); 0 WAL file(s) added, 0 removed, 0 recycled;
write=0.001 s, sync=0.001 s, total=0.025 s; sync files=0,
longest=0.000 s, average=0.000 s; distance=0 kB, estimate=0 kB;
LSN=0/14D0AD0, REDO LSN=0/14D0AD0

Regards,
Bharath Rupireddy.