Fix the addxml when add node after comment xml node

[JaynieBai]

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Fixes #11933

Context

<ItemGroup>
    <PackageReference Include="Newtonsoft.Json" Version="13.0.1" /><!-- some comment -->
  </ItemGroup>

dotnet add package Serilog --version 4.3.0 The trailing comment on the Newtonsoft.Json line is moved to the newly added package.

<ItemGroup>
  <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
  <PackageReference Include="Serilog" Version="4.3.0" /><!-- some comment -->
</ItemGroup>

Changes Made

If the reference element is immediately followed by a series of XML nodes, each of which does not contain any line breaks and is whitespace, a comment, or a processing instruction, then insert the new element after those nodes.

Testing

AddPackageReference_PreservesTrailingCommentOnSameLine

Notes