Improve BDD test output

[tobiasleibner]

Problem:
Currently, when the test output is printed, it only uses the test name, but not the test type. For the BDD test example from the README (modified to make it fail: https://godbolt.org/z/1T6bnzcez):

int main() {
  using namespace boost::ut;
  using namespace boost::ut::bdd;

  "vector"_test = [] {
    given("I have a vector") = [] {
      std::vector<int> v(5);
      expect((5_ul == std::size(v)) >> fatal);

      when("I resize bigger") = [=] {
        mut(v).resize(10);

        then("The size should increase") = [=] {
          expect(9_ul == std::size(v));
        };
      };
    };
  };
}

the output looks like this:

Running test "vector"... 
  Running test "I have a vector"... 
    Running test "I resize bigger"... 
      Running test "The size should increase"... FAILED
in: /app/example.cpp:17 - test condition:  [9 == 10]

Not that though we used given, when, then, the output always is the same ("Running test 'test name'") and does not reflect the BDD test structure.

Solution:
Include the test type in the test output. With this PR, the output becomes

Running test "vector"... 
  Running given "I have a vector"... 
    Running when "I resize bigger"... 
      Running then "The size should increase"... FAILED

This PR is based on #656 (to include the CI fixes from that PR), the only actual change in this PR is 41013d8.