Test Perl 5.12+ in CI

We use MX-Getopt, which in turn requires Getopt-Long-Descriptive, which now
requires 5.12+. You could actually still use most of TCM with earlier Perls,
but not the CLI tool.

See rjbs/Getopt-Long-Descriptive#40

Author: autarch

azure-pipelines.yml

@@ -15,7 +15,7 @@ stages:
       coverage: codecov
       debug: true
       test_xt: true
-      from_perl: 5.10
+      from_perl: 5.12
 
   - template: templates/helpers/macos.yml@ci-perl-helpers
     parameters: