Add both `[.]` and `[!hide]` tags when registering a hidden test case, as per documentation.
Co-authored-by: Martin Hořeňovský <martin.horenovsky@gmail.com>
b77cec05c0 fixed this problem for tagging tests, so that a test
case tagged with `[.foo]` would be parsed as tagged with `[.][foo]`.
This does the same for the test spec parsing.
Fixes#1798