Enable `png` based `ico` files and streams to be loaded into `Bitmap`

In PR #11375 we discovered that when converting `bmp` based `ico` resources to be `png` based, there was a failure when loading the icons as the `ToolboxBitmapAttribute` tries to create the resource as a `bitmap`. This errors out as `bitmap` uses different PInvokes from `Icon`, with `Icon` PInvokes supporting `png` for a few windows versions.

This would enable us to convert the `ico` files to be `png` based, saving a few megabytes in an AOT compiled app (#11370).