fix: prevent copying of the node_modules directory (#17331)

As noted in #16659, everything from `App_Plugins` is copied into the web
output. This is unneeded and in the case of the `node_modules` directory
unwanted behavior, these files are sources and not output that Umbracco
needs to serve packages/extensions.

The old behavior has led to many of the "path too long" errors we've
been seeing while building extensions.

Author: nul800sebastiaan

src/Umbraco.Cms.Targets/buildTransitive/Umbraco.Cms.Targets.targets

@@ -32,7 +32,7 @@
   <!-- Include App_Plugins content in output/publish directories -->
   <Target Name="IncludeAppPluginsContent" BeforeTargets="GetCopyToOutputDirectoryItems;GetCopyToPublishDirectoryItems">
     <ItemGroup>
-      <_AppPluginsFiles Include="App_Plugins\**" />
+      <_AppPluginsFiles Include="App_Plugins\**" Exclude="App_Plugins\**\node_modules\**" />
       <ContentWithTargetPath Include="@(_AppPluginsFiles)" Exclude="@(ContentWithTargetPath)" TargetPath="%(Identity)" CopyToOutputDirectory="PreserveNewest" CopyToPublishDirectory="PreserveNewest" />
     </ItemGroup>
   </Target>