feat(pytest): prefix diagnostic messages with parameterized test ID

[OddBloke]

Given a test like:

@pytest.mark.parametrize("a,b", [("b", "c"), ("c", "d")])
def test_a(a, b):
    assert False

This modifies the diagnostic message from:

neotest: assert False
neotest: assert False

to:

neotest: [b-c] assert False
neotest: [c-d] assert False

This is the same internal value which pytest uses for parametrized instances in its output, so it should be fully consistent.

Without this, the diagnostic messages aren't very useful for parametrized tests: you can't identify which of the multiple test which execute the given line are failing.

Fixes: #30

[rcarriga]

Love this thanks!