Use the hostapd_test_utils helper methods in

the Hostapd AIDL VTS tests.

At the beginning of each test, we now:
 1. Disable the Wifi framework, Hostapd, and Vendor HAL.
 2. Enable the Hostapd and Vendor HAL.

At the end of each test, we now:
 1. Disable the Hostapd and Vendor HAL.
 2. Enable the Wifi framework.

Bug: 283402709
Test: atest VtsHalHostapdTargetTest --iterations 10
       # Tested on both an Android T and U device.
       # All tests passed in both cases.
Change-Id: I8b5e24ad44d13fad09d84f1b212e60ca8df3aa7e