This adds support for templated tests and test methods via
`TEMPLATE_TEST_CASE` and `TEMPLATE_TEST_CASE_METHOD` macros. These
work mostly just like their regular counterparts*, but take an
unlimited** number of types as their last arguments.
* Unlike the plain `TEST_CASE*` macros, the `TEMPLATE*` variants
require a tag string.
** In practice there is limit of about 300 types.
