Add hid command support for uniq device attribute

Sony gamepads need a uniq attribute of a certain size in order to
obtain the MAC address, which makes our CTS test fail. This CL
adds the ability to define this attribute in our test definitions.

Bug: 314732730
Test: Compiles properly, will be tested together with the test
definition change in the same topic

Change-Id: I83203e8eb876b27d0e6e60adfbf6de3f4a6e9872