wpa_supplicant: Allow external management frame processing for testing

wpa_supplicant: Allow external management frame processing for testing

This enables more convenient protocol testing of AP and P2P
functionality in various error cases and unexpected sequences without
having to implement each test scenario within wpa_supplicant.
ext_mgmt_frame_handle parameter can be set to 1 to move all management
frame processing into an external program through control interface
events (MGMT-RX and MGMT-TX-STATUS) and command (MGMT_TX). This is
similar to the test interface that was added to hostapd previously, but
allows more control on offchannel operations and more direct integration
with the internal P2P module.

Signed-off-by: Jouni Malinen <j@w1.fi>