Add support for Debian 11 "bullseye"

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Is your feature request related to a problem? Please describe.

The test specs from ssh-baseline are failing with Debian 11 because this repo is missing the logic for handling Debian 11 and the ssh-baseline repo is partially implementing it.

Describe the solution you'd like

Being able to use this repo on Debian 11 with the default attributes. Debian 11 comes with openssh 8.4 (vs openssh 7.9 with Debian 10) so I assume the ciphers/MACs/KEXs need to be upgraded to leverage the new crypto.

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dev-sec/ssh-baseline#172 added support for openssh 8.X KEXs but it's missing the new ciphers and MACs.