HID service discovery refactor

This patch changes how HID is initialized.
Up till now, HID discovery was intricately chained,
to make sure two operations are not scheduled at same time.
From now on, all discovery is done and all operations are
scheduled for execution right away. There is separate set
of functions making sure all operations will be executed
without collisions.

This patch also removes BTA_HH_SCPP_INST_DEF, which was
used as hardcoded service id.

Bug: 27698756
Change-Id: I30a7388e129844c5e4727b2ed2b7c05867cc73a8