Use full namespace for builder field

[ugexe]

No description provided.

[ugexe]

zef has special-cased 'MakeFromJSON' for the time being. Some time in the near future you should be able to merge this with little fallout.

[ugexe]

@niner how shall we handle this in install-dist.pl? Do we do my $builder-class = first { *.so }, (try require ::("$name")), (try require ::("Distribution::Builder::$name") with a deprecation warning, or should we just cut straight to ::("$name")?

[ugexe]

install-dist.p6 will handle a full namespace or the original implied prefix version as of rakudo/rakudo@0249afc and the spec updated as of Raku/old-design-docs@26266b1 to reflect that using the full namespace is the new correct.