Maintains socket forward connections.

host-side socket_forward_proxy will keep a thread running that monitors
the adb connection to localhost:6520 + offset. If the connection is lost
due to adb daemon dying or the device not showing up in the adb devices
response, it will reconnect.

Bug: 79117228
Test: boot with host-adbd running and see the device appear in adb
devices. adb kill-server and wait for device to reappear in adb devices
Change-Id: Ia52fa04f19a2f2ca6b8496ff2f3e8f8f328cbe4f