The FIPS-supported algorithms added in
!207 may be too
restrictive. FIPS-supported algorithms may not be backwards compatible
with existing clients, such as those that are configured to use the
ssh-rsa (SHA-1 hash) key exchange algorithm.

This commit adds a `ssh.DefaultAlgorithms()` that returns mostly the
previous defaults used in FIPS, minus the elliptical curve algorithms,
which panic on the Go 1.24 FIPS compiler.

feat: add a relaxed list of FIPS default algorithms

See merge request !209



Merged-by: Steve Xuereb <sxuereb@gitlab.com>
Approved-by: Igor Drozdov <idrozdov@gitlab.com>
Approved-by: Steve Xuereb <sxuereb@gitlab.com>
Reviewed-by: Steve Xuereb <sxuereb@gitlab.com>
Reviewed-by: GitLab Duo <gitlab-duo@gitlab.com>
Co-authored-by: Stan Hu <stanhu@gmail.com>