Update .NET project files to copy local.settings.json only if exists

[anthonychu]

Add a conditional, otherwise it fails when running msbuild in CI pipelines.

<None Update="local.settings.json" Condition="Exists('local.settings.json')">
  <CopyToPublishDirectory>Never</CopyToPublishDirectory>
  <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
</None>

Edit: Looks like this might not work.

https://github.com/Azure/azure-functions-core-tools/issues/2252

[cataggar]

In F#, this does work for me. The difference is that F# is Include, not Update.

    <None Include="local.settings.json" Condition="Exists('local.settings.json')">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>

[aaronpowell]

Linking with PR #954 which shows a possible solution but has context as to the underlying issue