Bluetooth: HID: Add support for Set Idle and Get Idle Commands (3/4)

Provides an interface for application to send Set Idle
and Get Idle commands to remote HID Device. Support for these
two commands was missing from existing code, so existing code
design is reused to add support for these two commands.

Without this support following mandatory PTS test cases for HID 1.0
cannot be passed, TC_HOS_HID_BV_05/06.

Test: Executed PTS tests TC_HOS_HID_BV_05/06 and confirmed if they can
pass

Bug: 34344715
Change-Id: I548362cc328498920b2dae740f1a76b2cc2d6a67