Improve ParameterSet with nested ParameterSet objects

What's the problem this feature will solve?

I want the possibility to combinate ParameterSet objects to parametrize tests

Describe the solution you'd like

I want nested ParameterSet objects to be unpacked and combined their ids and marks
For example, I have this test:

@pytest.mark.parametrize(
    "a,b,c", [
        pytest.param(
            pytest.param(1, id="this_is_one"),
            pytest.param(2, id="this_is_two"),
            pytest.param(3, id="this_is_three"),
        )
    ]
)
def test_example(a, b, c):
    assert (1, 2, 3) == (a, b, c)

This test won’t pass now, because nested ParameterSet objects throw in the test "as-is".

FAILED test.py::test_example[a0-b0-c0] - AssertionError: assert (1, 2, 3) == (ParameterSet...)

This is logical behavior, but useless.

I suggest unpack nested ParameterSet objects and merge their ids and marks. If parent ParameterSet has an id - it rewrites nested ids.
The example above will in collect:
<Function test_example[this_is_one-this_is_two-this_is_three]>

Here are a few more examples

1. ID rewriting

@pytest.mark.parametrize(
    "a,b,c", [
        pytest.param(
            pytest.param(1, id="this_is_one"),
            pytest.param(2, id="this_is_two"),
            pytest.param(3, id="this_is_three"),
            id="one_two_three"
        )
    ]
)

<Function test_example[one_two_three]>

2. Use simple values with ParameterSet

@pytest.mark.parametrize(
    "a,b,c", [
        pytest.param(
            1,
            pytest.param(2, id="this_is_two"),
            3,
        )
    ]
)

<Function test_example[1-this_is_two-3]>

3. Merge marks

@pytest.mark.parametrize(
    "a,b,c", [
        pytest.param(
            pytest.param(1, id="this_is_one", marks=[pytest.mark.one]),
            pytest.param(2, id="this_is_two", marks=[pytest.mark.two]),
            pytest.param(3, id="this_is_three", marks=[pytest.mark.three]),
            id="one_two_three",
            marks=[pytest.mark.full]
        )
    ]
)

In this case, marks merged in one list - [one, two, three, full]

I have a solution that works, but I wrote it "on a napkin" - https://github.com/vgorkavenko/pytest/commit/99c0712c5ec40773369ce1d6fc4cf60724544136

Start by tracing pytest.mark.parametrize and ParameterSet handling, then review the referenced napkin solution commit. Done means nested ParameterSet values are unpacked, nested and parent ids are combined with parent ids taking precedence, and marks from all levels are merged without changing simple-value behavior.