iKey is not read from appsettings.json or environment when using AddApplicationInsightsTelemetry()

[cijothomas]

If you are reporting bug/issue, please provide detailed Repro instructions.

Repro Steps

1. VS->New WebApp .net core

2. Add the following to appsettings.json
   {
   "Logging": {
   "IncludeScopes": false,
   "Debug": {
   "LogLevel": {
   "Default": "Warning"
   }
   },
   "Console": {
   "LogLevel": {
   "Default": "Warning"
   }
   }
   },
   "ApplicationInsights": {
   "InstrumentationKey": "11111111-2222-3333-4444-555555555555"
   }
   }

3. Enable AI by using AddApplicationInsightsTelemetry(). (Do not pass ikey as argument)

4. Start app (with or without VS Debugger), and put load.

Actual Behavior

5. Ikey is not read, and hency no telemetry sent.

Expected Behavior

Ikey should be read from appsettings.json

Version Info

SDK Version : 2.2
.NET Version :
How Application was onboarded with SDK(VisualStudio/StatusMonitor/Azure Extension) : VS
OS : Windows
Hosting Info (IIS/Azure WebApps/ etc) : Self

[cijothomas]

Originally reported here:
#585 (comment)

[cijothomas]

Closed with #670