Display derived minimum required perl version

[grr]

Describe the feature

Currently metacpan will display the minimum perl version only if it is included by the author. But this data is often missing or inaccurate. Examining the minimum perl version of the dependency chain and even the testers data will get us a lot closer to a useful value. Though we can't do anything about the case where the author has artificially inflated the value since installation tools respect the value.

Which problem does it solve?

Give user more accurate information of whether a distribution will work on their version of Perl.

Expected behavior

With the data metacpan has at hand, it can give a better estimate of the minimum required Perl version.