gralloc: Add QtiMapperExtensions

This change moves extensions to QtiMapperExtensions to decouple
it from IMapper revisions. The function
QtiMapper::getMapperExtensions() is used to access the extensions
through a mapper instance. QtiMapper revision is incremented to
2.0 to reflect the change.

CRs-Fixed: 2451975
Change-Id: I7043bd380e9b7b3ea8d9bac4da3e886a5d46b631
8 files changed