LU-17015 gss: remove legacy sunrpc-cache based gss caches

LU-17015 gss: remove legacy sunrpc-cache based gss caches

Now that GSS caches are based on Lustre's internal upcall cache
mechanism, we can remove the legacy ones based on the sunrpc cache
implementation, as this code is unused.

We can also remove support for updated get_expiry() in Linux 6.3, as
this function is no longer used.

Test-Parameters: trivial
Test-Parameters: kerberos=true testlist=sanity-krb5
Test-Parameters: testgroup=review-dne-selinux-ssk-part-2
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I98d8777d225c723ae061ef360011abfc092e09d8
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52376
Reviewed-by: Aurelien Degremont <adegremont@nvidia.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>