egl: use device dispatch if at least one vendor suceeds
Currently, in InitDeviceListInternal if any egl vendor fails to list its devices for any reason the construction of the device list is abandoned. That means that even if we have one vendor successfully serving the application, the failure of another vendor library will break any api calls related to egl devices. Instead, if a vendor fails queryDevicesEXT the device mapping logic should proceed as if it listed no devices. If the relevant device belongs to the failed vendor then the dispatch will still fail with EGL_BAD_DEVICE.