Side effects of switching to FrameworkReference

[TimothyMothra]

This issue is to track extra changes due to #2355

We're switching projects to use FrameworkReference wherever possible. link

Several AspNetCore packages will no longer be published in favor of FrameworkReference.
This simplifies our dependencies and ensures that we're always using the latest version of a library.

This change had some conflicts in our test projects.

• AzureInstanceMetadataEndToEndTests depends on AzureInstanceMetadataServiceMock which creates an in-proc server to handle HTTP requests.
  This is being addressed in a separate issue AzureInstanceMetadata: replace tests #2357

• Microsoft.ApplicationInsights.AspNetCore.Tests.csproj

  'IHostingEnvironment' is obsolete: 'This type is obsolete and will be removed in a future version.
  The recommended alternative is Microsoft.AspNetCore.Hosting.IWebHostEnvironment.'

[TimothyMothra]

closing this. i moved these details back into #2251