Read from META.json rather than META.yml if available

[perlpunk]

META.json is more recent and supports things like dual licenses, e.g.
https://metacpan.org/source/DCANTRELL/Data-Compare-1.27/META.json#L8
In such cases the META.yml generated by ExtUtils::MakeMaker is wrong.

[perlpunk]

This should be fixed soon.
Another example is:
https://metacpan.org/source/EZIMUEL/Search-Elasticsearch-7.30/Makefile.PL#L59
https://metacpan.org/source/EZIMUEL/Search-Elasticsearch-7.30/META.json
Modules like Test::Deep are only listed in TEST_REQUIRES and in META.json, and cpanspec apparently doesn't read any of those.

Not fixing this will create more and more manual work for d:l:p maintainers.

[perlpunk]

Some authors even start to remove META.yml and only provide META.json: https://domm.plix.at/perl/2021_04_two_dist_zilla_questions.html

[perlpunk]

This is an example where the license in META.json says gpl3 and META.yml says gpl. According to the pod, gpl3 is the correct one:
https://metacpan.org/source/GSB/Astro-FITS-Header-3.08/META.json#L13
https://metacpan.org/source/GSB/Astro-FITS-Header-3.08/META.yml#L15