Improve user convenience of the rcirc debug buffer

* lisp/net/rcirc.el (rcirc-debug): Ignore rcirc-debug-buffer read-only
status.  Restore point after insertion unless it was at the end.
Ensure a newline before each [lead].  Replace %Y-%m-%d with the
equivalent %F in format-time-string; remove useless concat.  (Bug#32470)
1 job for master in 52 minutes and 7 seconds (queued for 2 seconds)
Status Job ID Name Coverage
failed #1775


Name Stage Failure
test-all Test
Makefile:318: recipe for target 'check-doit' failed
make[2]: *** [check-doit] Error 1
make[2]: Leaving directory '/builds/emacs/emacs/test'
make[1]: *** [check-expensive] Error 2
Makefile:293: recipe for target 'check-expensive' failed
make[1]: Leaving directory '/builds/emacs/emacs/test'
make: *** [check-expensive] Error 2
Makefile:957: recipe for target 'check-expensive' failed
ERROR: Job failed: exit code 1