binder: Add network request/response interface

1. Add a callback function in |INetworkCallback| to make
any control requests on the corresponding network to registered
callback clients.
2. Add a function in |INetwork| to send responses to the above
request from the clients.

These are used when there is a need to perform external
SIM authentication for example.

While there, fix a nit:
Network.SetSSID() is setting a regular byte array field and
not a key field.

BUG: 30815238
TEST: This will have to wait for wificond integration for testing.

Change-Id: I8bfb9c381159373697ae8d1a0d7b999fca19b3a9
Signed-off-by: Roshan Pius <rpius@google.com>
9 files changed