remove deprecated driver_async_cancel function

Some time ago the driver_async_cancel function was deprecated and slated
for removal in R17. This commit removes the function along with its
associated tests and documentation, increments the
ERL_DRV_EXTENDED_MAJOR_VERSION to 3 and ERL_DRV_EXTENDED_MINOR_VERSION to
0, and modifies the sys_info_base_drv and sys_info_prev_drv tests in the
driver test suite to check version 3.0 instead of 2.0.