Implement "WanLinkStatus" event handler, REF 15326

Voice HAL is expected to handle the rpc request (from TVM):

"module":"voicehal",
"version":"0.0.1",
"reqId":"00023529",
"action":"setParameters",
"params":[
{
"name":"WanLinkStatus",
"type":"unsignedInt",
"value":1
}
]
}

Please pay attention that "setParameters" is used to set TR parameter values, however, "name":"WanLinkStatus" doesn't follow the standard TR path. The solution: declare WanLinkStatus under standard TR path Device.Services. and add special parsing of this "set" request in "setParameters" rpc handler. This is a workaround but the easiest solution, requiring less effort, otherwise we would need to implement separate handlers for normal set requests and for the events (like "WanLinkStatus", the only one so far) that are not in the standard TR tree.