Make removal of built-in modules possible #633

As an example,
DependencyCollectorTelemetryModule is injected into DI Container in a lazy way(https://github.com/Microsoft/ApplicationInsights-aspnetcore/blob/develop/src/Microsoft.ApplicationInsights.AspNetCore/Extensions/ApplicationInsightsExtensions.cs#L142). This makes it difficult for customer to remove the module from the collection in the ConfigureServices method, as it wont be present yet.

Repro Steps

1. Follow this steps and attempt to remove DependencyCollector module https://github.com/Microsoft/ApplicationInsights-aspnetcore/wiki/Dependency-Tracking-and-Performance-Counter-Collection#disabling-telemetry-module-services

Actual Behavior

DependencyCollector won't be removed.

Expected Behavior

DependencyCollector should be removed.

Version Info

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