This means mutiple generic generators and some inference helper
* take(n, generator)
* filter(predicate, generator)
* map(func, generator)
* repeat(generator, repeats)

By using non-trivially copyable types, we force libstdc++-9's variant to
properly enter the valueless-by-exception state for our stringification
test.

Related to #1511

support for generating test cases based on multiple template template
types combined with template arguments for each of the template template
types specified

e.g.
```
TEMPLATE_PRODUCT_TEST_CASE("template product","[template]",
			   (std::tuple, std::pair, std::map),
			   ((int,float),(char,double),(int,char)))
```
will effectively create 9 test cases with types:
std::tuple<int,float>
std::tuple<char,double>
std::tuple<int,char>
std::pair<int,float>
std::pair<char, double>
std::pair<int,char>
std::map<int,float>
std::map<char,double>
std::map<int,char>

Tested type is accessible in test case body as TestType
Unique name is created by appending ` - <index>` to test name
since preprocessor has some limitations in recursions

Closes #1454

The previous implemetation was just plain broken for most of
possible uses, the new one should work (even though it is ugly
as all hell, and should be improved ASAP).

Fixes #1436

Fixes #1438