Avoid Attribute.GetCustomAttributes overheads when inherit==true is useless

[stephentoub]

Just stop doing unnecessary work.

Method	Toolchain	Mean	Ratio	Allocated
Get	\main\corerun.exe	826.7 ns	1.00	664 B
Get	\pr\corerun.exe	488.1 ns	0.59	104 B

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
using System;
using System.Reflection;

[MemoryDiagnoser]
public class Program
{
    static void Main(string[] args) => BenchmarkSwitcher.FromAssemblies(new[] { typeof(Program).Assembly }).Run(args);

    private PropertyInfo _prop = typeof(B).GetProperty("MyProp");

    [Benchmark]
    public Attribute[] Get() => Attribute.GetCustomAttributes(_prop, inherit: true);
}

class A { }

class B : A
{
    [My]
    public int MyProp { get; set; }
}

class MyAttribute : Attribute { }

[jkotas]

Failure is #54125

[stephentoub]

Failure is #54125

Thanks. I kept trying to figure out how my changes were causing these :)