Allow tagging by TestType in TEMPLATE_TEST_CASE

[torrance]

Description

In my own use case, I run tests of the kind:

TEMPLATE_TEST_CASE("MyTest", "[tag1][tag2]", float, double} {
    [...]
}

where the tests are parameterised by the floating point precision.

I would love the ability to run just the float tests, or just the double tests, for example. However, at present it does not seem possible to tag by the TestType.

Feature request: allow for TestType to be used in the tag list, e.g.

TEMPLATE_TEST_CASE("MyTest", "[tag1][tag2][TestType]", float, double} {
    [...]
}

thus allowing me to run: ./tests [float] or ./tests [double].