Tweak the warning display to be less like a TLS decoding page

* lisp/net/nsm.el (nsm-parse-subject, nsm-certificate-part):
Restore functions for parsing subjects.
(nsm-format-certificate): Use them to display more user-friendly
data.  Also change the display to have fewer lines again so that
the data of interest isn't pushed off the screen.
1 job for netsec in 28 minutes and 10 seconds (queued for 3 seconds)
Status Job ID Name Coverage
failed #3083


Name Stage Failure
test Test
make[2]: *** [check-doit] Error 1
Makefile:300: recipe for target 'check-doit' failed
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:270: recipe for target 'check' failed
make[1]: *** [check] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:947: recipe for target 'check' failed
make: *** [check] Error 2
ERROR: Job failed: exit code 1