TracerProviderSdk expects that ActivtyProcessor is Disposable

[eddynaka]

Describe your environment. Describe any aspect of your environment relevant to the problem:

• SDK version: (nuget versions of the all the relevant packages): master branch
• .NET runtime version (.NET or .NET Core, TargetFramework in the .csproj file): any
• Platform and OS version: any

If you're reporting a problem with a specific version of a library in this repo, please check whether the problem has been fixed on master.

opentelemetry-dotnet/src/OpenTelemetry/Trace/TracerProviderSdk.cs

Lines 53 to 56 in b741947

	if (this.ActivityProcessor is IDisposable disposableProcessor)
	{
	disposableProcessor.Dispose();
	}

Steps to reproduce.
If we run Examples.Console -> console type in release, no data will be printed

What is the expected behavior?
If we run Examples.Console -> activity would be printed

What is the actual behavior?
If we run Examples.Console -> no data printed

Additional context.
Today, ActivityProcessor isn't implementing IDisposable

[eddynaka]

Assign me when possible. I will take a look at this.