Review and tidy up param types

[nward]

There are a lot of param types which are not quite right, for example:

• Variants with types which cover one another, where doing so is not beneficial for documentation
• Params with Optional type, but a default that is not undef
• Params with types which should be more specific, for example freeradius::sql::server should have Stdlib::IP::Address::Nosubnet, as a prefix does not make sense here