Standardize links for methods in docs.

[coke]

There are many instances of linking to methods of certain types. Need to standardize on the link, something like:

the L<C<Str.Int> method|/type/Str#method_Int>

Do we allow secondary links to https://docs.raku.org/routine/Int?

Whatever the solution, we need to make sure that xt/rakudoc-types.rakutest doesn't fail on these. (and validates them if it can)