FIPS SSH key configuration settings

What does this MR do and why?

Describe in detail what your merge request does and why.

Updates the SSH key configuration settings for running in FIPS mode. This adjusts the defaults applied to the key restrictions, preventing unrestricted key lengths, and reducing the number of available options. I'm not currently sure that this is the correct set of restrictions, but that can be updated later.

This is likely only a part of the changes required for this feature, but I'd like to keep this MR from expanding much further.

Related #325172 (closed)

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