fix(ci): skip published cpan libs and fix promote-deb index read (backport master)

[tuntoja]

Fixes CTOR-2557

Backport to master of #6458 plus the promote-deb fix of #6462, needed to finish the release-20260900 stable promotion.

Description

• Cherry-pick of ci(perl-cpan-libraries): skip libraries already published in stable #6458 (clean, identical diff to develop): release/hotfix cpan matrix compared with stable, unchanged libs are no longer rebuilt nor delivered
• Without it, the release build rebuilt every lib, the testing delivery refused them (already in stable) and the promotion found nothing to promote
• promote-deb: the testing Packages index is read from a temp file instead of a pipe into awk ... exit
• The pipe made every deb promotion fail with curl: (23) (awk closes it on the first match while curl still writes, fatal under pipefail)
• Once merged: rerun the failed deb promotion jobs of connector-vmware and plugins (run 36551686457)