Implement PacketStream RGMII receiver

[JLaumen]

Feature description
This component adapts the RGMII receiver to the PacketStream protocol. This will involve writing a Protocol for the RGMII receive type and wrapping it. The RGMII receiver cannot handle back pressure since it's not possible to tell Ethernet to stop receiving, thus it should have unsafe in its name. An important part of this component is that it needs to assert last on the last byte of the incoming byte stream. This can be detected by checking the next transfer contains no byte and the current transfer contains a byte.

Expected behaviour
The bytes coming from the RGMII receiver are the same as the one in the PacketStream. With the last asserted as the end of the packet.

Additional Context