Add "Open XEL file" support to profiler in sqltoolsservice (#2091)

* Open XEL file changes

* placeholders for openxel

* add observable xe reader

* md format tweaks

* implement localfile as a new session type

* add ErrorMessage to session stopped notice

* fix flaky test

* handle already running session

* fix stopped session event send on file completion

* fix flaky unit test

* Update XElite and dependent versions

* Fix errors after merge and remove failing tests for now

* Fix main merge mess-up.
Address comments.
Add one more relevant test.

* Remove extra namespace.

* Remove unnecessary import

* Fix build error

* Address comments.

* Remove disabiling JSON002 compiler warning

* Address comments and update json handling

* Fix build error

* Fix integration test (emerged due to Main merge mess up)

* Clean up code (no functional changes)

---------

Co-authored-by: Karl Burtram <karlb@microsoft.com>
Co-authored-by: shueybubbles <david.shiflet@microsoft.com>

test/Microsoft.SqlTools.ServiceLayer.UnitTests/Microsoft.SqlTools.ServiceLayer.UnitTests.csproj

@@ -45,4 +45,9 @@
 	<ItemGroup>
 		<EmbeddedResource Include="ShowPlan\TestShowPlanRecommendations.xml" />
 	</ItemGroup>
+	<ItemGroup>
+	  <None Update="Profiler\TestXel_0.xel">
+	    <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+	  </None>
+	</ItemGroup>
 </Project>