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
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:93a4c0fbdc14d99cbd382fd50be83b7058ca6b56

)
Merged-In: I83203e8eb876b27d0e6e60adfbf6de3f4a6e9872
Change-Id: I83203e8eb876b27d0e6e60adfbf6de3f4a6e9872
Signed-off-by: Edward Liaw <edliaw@google.com>