Move board_config_wifi.mk to external/wpa_supplicant_8

Bug: 395976122
Test: m hostapd_cli hostapd libhostapd_aidl wpa_cli wpa_supplicant \
        wpa_supplicant_macsec libwpa_client libwpa_aidl libpasn
Ignore-AOSP-First: The related CLs is only in internal currently

Change-Id: I2d4a2d432688c40b7b59aba7fe61dcbc4d413e6a