Merge patch series "b4 keyring maintenance"

Uwe Kleine-König <u.kleine-koenig@baylibre.com> says:

last week I noticed that there are several symlinks in .keyring (i.e.
the directory that can be used with b4) that are not up to date. This
patch set cleans up a part of the issues.

patch #1 just adds --gen-b4-keyring to the example script as this is
what Konstantin seems to use.
patch #2 removes all data for removed keys. patch #3 removes all data
for revoked UIDs.

What is still open and ugly:

 - The scripts don't cope for these cases, so unless some manual care is
   applied, the keyring will become outdated again.
 - There are quite some email addresses that are part of two keys
   (`iconv -f latin1 keys/*.asc | sed -nr 's/^uid[^<]*<([^>]*)>/\1/p' | sort | uniq -d`
   produces some false positives)
   For these the cert that is linked to is not chosen deterministically.

Link: https://patch.msgid.link/cover.1770141846.git.u.kleine-koenig@baylibre.com
Signed-off-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>