Update fakes version (#15227)

Update the version of the fakes assembly that is used to resolve runsettings. Also, update the TestRunnerHarness package to an 18.0.0.0 version.

Author: drognanar

eng/Versions.props

@@ -51,7 +51,7 @@
     <MicrosoftDiagnosticsNETCoreClientVersion>0.2.631904</MicrosoftDiagnosticsNETCoreClientVersion>
     <MicrosoftExtensionsDependencyModelPackageVersion>6.0.2</MicrosoftExtensionsDependencyModelPackageVersion>
     <MicrosoftExtensionsFileSystemGlobbingVersion>6.0.0</MicrosoftExtensionsFileSystemGlobbingVersion>
-    <MicrosoftFakesVersion>17.12.0</MicrosoftFakesVersion>
+    <MicrosoftFakesVersion>18.0.0-beta.25364.2</MicrosoftFakesVersion>
     <MicrosoftInternalCodeCoverageVersion>17.15.0-preview.25354.5</MicrosoftInternalCodeCoverageVersion>
     <!--
       Make sure you are taking a version from a release branch (rel/d*) in VS. Otherwise there won't be symbols for the dlls in package,

src/Microsoft.TestPlatform.Common/ExternalAssemblyVersions.cs

@@ -10,5 +10,5 @@ internal class ExternalAssemblyVersions
     /// Microsoft.QualityTools.Testing.Fakes.TestRunnerHarness package.
     /// The Package version can be found in "eng\Versions.props"
     /// </summary>
-    internal const string MicrosoftFakesAssemblyVersion = "17.0.0.0";
+    internal const string MicrosoftFakesAssemblyVersion = "18.0.0.0";
 }