Bound attribute keys don't maintain HTML provided case in TagHelperContext.AllAttributes

[NTaylorMullen]

When generating code for TagHelpers, bound attributes are added to the TagHelperContext.AllAttributes collection with their TagHelperDescriptor name.

Example:

<foo bAr="123" />

public class FooTagHelper : TagHelper
{
    public int Bar { get; set; }

    public override void Process(TagHelperContext context, TagHelperOutput output)
    {
        // Outputs "bar", expected output is "bAr"
        Console.WriteLine(context.AllAttributes.First(kvp => kvp.Key.Equals("BAR", System.StringComparison.OrdinalIgnoreCase)).Key);
    }
}