Expose function level TraceWriter to Binding Extensions

TraceWriter in [ScriptBindingProvider](https://github.com/Azure/azure-webjobs-sdk-script/blob/dev/src/WebJobs.Script.Extensibility/ScriptBindingProvider.cs) and ExtensionConfigContext are host level trace writers. We need a TraceWriter that can log at function level
#### Repro steps

Provide the steps required to reproduce the problem

EnableTestSend on NH output binding:

{
"type": "notificationHub",
"name": "notification",
"hubName": "scripthub",
"connection": "scripthub_NOTIFICATIONHUB",
"direction": "out",
"enableTestSend": true,
"platform": "wns"
}
#### Expected behavior

NH debug logs show up in logs window
#### Actual behavior

NH debug logs show up in LogStream
#### Known workarounds

N/A
#### Related information

Provide any related information
- Programming language used
- Links to source

Start by reading src/WebJobs.Script.Extensibility/ScriptBindingProvider.cs and the ExtensionConfigContext references to understand the existing host-level TraceWriter behavior. Trace the notificationHub binding scenario with enableTestSend enabled and compare the logs window with LogStream. Done means binding-extension debug logs appear at function level in the logs window rather than only in LogStream.

Written by the indexing model from the issue text.