Add an API for Multi-Link Operation mode

OEM can use the new system API to set Multi-Link Operation mode as low
latency, high throughput, low power or default. Get API returns the
current Multi-Link Operating Mode.

Bug: 268235139
Test: atest android.net.wifi.WifiManagerTest#testMloMode
      atest com.android.server.wifi.WifiServiceImplTest#testGetMloMode
      atest com.android.server.wifi.WifiServiceImplTest#testSetMloMode

Change-Id: Ifaeebb7840c506d27b0e811085760540eb1291b3
13 files changed