CI: Improve dist-modules (group output + continue on error)

[bram-perl]

Highlights:

• Group the output per dist (before there was no grouping so all output was in one big block)
• Continue when one dist fails (before it would stop after the first failure)

(Details: see commit message)

Example runs:

• no failure: https://github.com/bram-perl/perl5/actions/runs/3070729590/jobs/4960754562
• 1 failure: https://github.com/bram-perl/perl5/actions/runs/3070682723/jobs/4960655118
• 2 failures: https://github.com/bram-perl/perl5/actions/runs/3070645332/jobs/4960579443