Use authentication tokens for PM GitLab runner

Starting with GitLab 16, there is a new mechanism to authenticate the
runners via authentication tokens, so use it instead.  Older tokens and
runners are also removed, as they are no longer used.

With the new way of managing tokens, both the tags and the locked state
are managed from the GitLab web page.

See: https://docs.gitlab.com/ee/ci/runners/new_creation_workflow.html
Reviewed-by: Aleix Boné <abonerib@bsc.es>

secrets/gitlab-runner-docker-token.age

@@ -0,0 +1,9 @@
+age-encryption.org/v1
+-> ssh-ed25519 HY2yRg WvKK6U1wQtx2pbUDfuaUIXTQiCulDkz7hgUCSwMfMzQ
+jLktUMqKuVxukqzz++pHOKvmucUQqeKYy5IwBma7KxY
+-> ssh-ed25519 CAWG4Q XKGuNNoYFl9bdZzsqYYTY7GsEt5sypLW4R+1uk78NmU
+8dIA2GzRAwTGM5CDHSM2BUBsbXzEAUssWUz2PY2PaTg
+-> ssh-ed25519 MSF3dg T630RsKuZIF/bp+KITnIIWWHsg6M/VQGqbWQZxqT+AA
+SraZcgZJVtmUzHF/XR9J7aK5t5EDNpkC/av/WJUT/G8
+--- /12G8pj9sbs591OM/ryhoLnSWWmzYcoqprk9uN/3g18
+<EFBFBD><EFBFBD><EFBFBD>
<01>‡%<25>]yi"<22><><EFBFBD>L<EFBFBD><0B><>H`<60>a$<24><>)<29>9ve<76>.0<EFBFBD>m<EFBFBD>K<EFBFBD>v<EFBFBD><EFBFBD><0B>u"|1c<31>-%<25><>"<22>WF<12><><EFBFBD>A<EFBFBD><41>h<EFBFBD>$<05><>j<e<><65>x<EFBFBD>Lx<4C><78>.?<3F><><EFBFBD>:L<><4C><EFBFBD><EFBFBD>,<2C>u<EFBFBD>|<7C><>F|<7C>i<EFBFBD><69><EFBFBD>