Add ClassDataItemIterator::HasNextMethod

Returns true if there are either static of virtual methods remaining,
changed most places to use this where possible.

Slight behavioral change for duplicate method checking, we not
persist the method index across the static method / virtual method
boundary.

Motivation: Generic cleanup to remove copy paste.

Test: test-art-host
Change-Id: I7a1b507e681b2c40452f8a9913b53a96b181e171