[GITHUB-9193] Resolve erroneous types in diamond-base new class expressions.

[lahodaj]

Consider code like:

package test;
public class Test {
    public static class Test<T> {
        public Test(T value) { }
        public Test(String name, T value) { }
    }
    private static void test() {
        new Test<>/*CC here*/
    }
}

Invoking code completion at the marked place leads to an empty result. The issue is that when the new Test<> is attributed, it gets an erroneous type. I don't think there's currently a good argument to change the attribution, but the original type of the erroneous type is a usable type, so we can use that original type, and things should work.

The bug report says there's a difference between custom and JDK classes, but looking into that deeper, that's not the case. But there's a difference between classes that have a no-arg constructor, and those that only have constructors with arguments. The latter ones don't currently work, and would hopefully be fixed by this PR.

Closes #9193

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[mbien]

thanks!