Switch uint{8,16,32,64} to use yang.common.Uint{8,16,32,64}

Our current mapping of unsigned types to java.lang widens them to accommodate to the increased range. This is quite wasteful in case of uint32 (24 bytes instead of 16) and uint64 (64 bytes instead of 24).

This type overlap also does not play well with MD-SAL Binding, as it causes uncompilable code for unions – see MDSAL-330.

Address these concerns by switching unsigned types to use yang.common.Uint* classes, which provide this encapsulation.