Really check for unused variables

[bschmalhofer]

Currently unused variables are detected with Variables::ProhibitUnusedVariables. But this check is very limited. Olaf Alders did a write up of the various ways of improving this, https://www.olafalders.com/2022/02/22/finding-unused-perl-variables/. I think it makes sense to add Code::TidyAll::Plugin::Test::Vars to the code policy.

[bschmalhofer]

The next step would be to activate https://metacpan.org/pod/Perl::Critic::Policy::Variables::ProhibitUnusedVarsStricter .

[stefanhaerter]

Strongly in favor of progressing to this.

[stefanhaerter]

Current state at time of writing, referring to rel-11_1 HEAD:

• 708 violations in scripts/
• 403 violations in Kernel/
• 2 violations in bin/