wifi: Use hal_tool & if_tool

Changes in the CL:
1. Currently |WifiNative.cpp|, uses |hal_tool| to initialize the
function table and |if_tool| to set the interface up when |startHAL|
method is invoked. Use the same sequence in the HIDL'ized HAL.
2. Remove the assertion if the function table initialization fails. This
will result in a failure indication on starting the HAL now.

Bug: 31352200
Test: mmma -j32 hardware/interfaces/wifi/1.0/default
Change-Id: I268845ed62158b6a2ff36659f0bb15c4100a7222