Allow override method/property for ParamsSource

[neuecc]

Currently, when specifying abstract properties or methods with ParamsSource, an exception occurs with SingleOrDefault:
System.InvalidOperationException: Sequence contains more than one matching element

BenchmarkRunner.Run<Bench>();

public abstract class BenchBase
{
    public abstract int[] Levels { get; }

    [ParamsSource(nameof(Levels))]
    public int Level { get; set; }

    [Benchmark]
    public void Foo()
    {
    }
}

public class Bench : BenchBase
{
    public override int[] Levels => [1, 2, 3];

    [Benchmark]
    public void Bar()
    {
    }
}

This is because sourceType.GetAllMethods() and sourceType.GetAllProperties() traverse up the parent class hierarchy, enumerating both the overridden property and abstract property with the same name.
And since GetValidValuesForParamsSource processes with SingleOrDefault, the exception occurs.

Since the enumeration starts from sourceType in order, this should be safe to change to FirstOrDefault as the best match.

[timcassell]

Can you add an integration test for that?

[neuecc]

Thank you for checking quickly!
I've added tests.

[timcassell]

Thanks @neuecc!