Add @hide support for styleable attributes

AAPT2 generates documentation for styleables. The documentation contains
references to the attributes of the styleable. If the attributes are
marked @hide, remove the references to the attributes in the generated
coments.

Bug: 120262117
Test: m -j offline-sdk-docs
Change-Id: I541002077b17771d89caead04df2f4ae66c623f0