add a new 2021 roadmap item for Puppet

Working on and improving our Puppet environment while following best
practices [0] is currently blocking on our lack of an external node
classifier, or ENC. Adding this item as a priority on our roadmap will
resolve team#40358 and help advance team#29387

Deploying `hiera-enc` in itself should be fairly straightforward,
however since some nodes are assigned multiple roles, some of those
roles (eg. roles::fde) will have to be converted into profiles instead
and included from the role class. So a small amount of restructuring of
our roles manifests and current hiera data is to be expected.

If I can focus on this I don't expect it should take more than one
week's time (20h) to implement this fully.

[0] https://puppet.com/docs/puppet/7/the_roles_and_profiles_method.html
1 job for !16 with add-puppet-enc in 25 seconds (queued for 3 seconds)
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