When Assert.Multiple is found, should suggest to convert to Assert.EnterMultipleScope

[OsirisTerje]

A new rule should be made that helps the user to convert from Assert.Multiple to Assert.EnterMultipleScope.

Also see issue #865

[mikkelbu]

Looking at https://docs.nunit.org/articles/nunit/writing-tests/assertions/multiple-asserts.html it is essentially changing

Assert.Multiple(() =>
{
    ClassicAssert.AreEqual(5.2, result.RealPart, "Real Part");
    ClassicAssert.AreEqual(3.9, result.ImaginaryPart, "Imaginary Part");
});

into

using (Assert.EnterMultipleScope())
{
    ClassicAssert.AreEqual(5.2, result.RealPart, "Real Part");
    ClassicAssert.AreEqual(3.9, result.ImaginaryPart, "Imaginary Part");
}