New test custom--test-theme-variables

* test/lisp/custom-tests.el (custom--test-user-option)
(custom--test-variable): New variables.
(custom--test-theme-variables): New test.

* test/lisp/custom-resources/custom--test-theme.el (custom--test):
New file.
1 job for master in 43 minutes and 45 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #522
test-all

00:43:45