Move vendor data helper functions to

wifi_aidl_test_utils.

Allows these methods to be used for
VTS tests across all Wifi HAL services.
Previously, they were only available to
the Supplicant tests.

Bug: 322815584
Test: atest VtsHalWifiSupplicantStaNetworkTargetTest \
            VtsHalWifiSupplicantP2pIfaceTargetTest
Change-Id: I2ef8fe528aa35bc2109a0f845432dec88962f21b