Revert "Add ActivitySource support to DiagnosticsHandler (#54437)" (#55006)

This reverts commit c88da29.

Author: MihaZupan

src/libraries/System.Net.Http/src/ILLink/ILLink.Substitutions.xml

@@ -1,7 +1,7 @@
 <linker>
   <assembly fullname="System.Net.Http">
     <type fullname="System.Net.Http.DiagnosticsHandler">
-      <method signature="System.Boolean get_IsGloballyEnabled()" body="stub" value="false" feature="System.Net.Http.EnableActivityPropagation" featurevalue="false" />
+      <method signature="System.Boolean IsGloballyEnabled()" body="stub" value="false" feature="System.Net.Http.EnableActivityPropagation" featurevalue="false" />
     </type>
     <type fullname="System.Net.Http.HttpClient">
       <method signature="System.Boolean IsNativeHandlerEnabled()" body="stub" value="true" feature="System.Net.Http.UseNativeHttpHandler" featurevalue="true" />

src/libraries/System.Net.Http/src/System.Net.Http.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <WindowsRID>win</WindowsRID>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
@@ -494,6 +494,7 @@
   <!-- Common -->
   <ItemGroup>
     <Compile Include="System\Net\Http\DiagnosticsHandler.cs" />
+    <Compile Include="System\Net\Http\DiagnosticsHandlerLoggingStrings.cs" />
     <Compile Include="System\Net\Http\SocketsHttpHandler\SocketsHttpPlaintextStreamFilterContext.cs" />
     <Compile Include="$(CommonPath)System\Threading\Tasks\TaskCompletionSourceWithCancellation.cs"
              Link="Common\System\Threading\Tasks\TaskCompletionSourceWithCancellation.cs" />