Add support for configuring sources

[julealgon]

We have a scenario today where we restore packages in CI/CD without a nuget.config file, but still need to fetch from our own GitHub NuGet feed. Being able to directly configure a package source as part of this action would significantly simplify our workflow at the moment, which looks like this:

      - name: Setup NuGet
        uses: nuget/setup-nuget@v4

      - name: Remove Application NuGet Source
        env:
          Package_Source_Name: github
        continue-on-error: true
        run: |
          nuget sources remove `
            -Name $env:Package_Source_Name `
            -NonInteractive

      - name: Configure Application NuGet Source
        env:
          Package_Source_Name: github
          Package_Source_Url: {our_feed_url}
        run: |
          nuget sources add `
            -Name $env:Package_Source_Name `
            -Source $env:Package_Source_Url `
            -Username ${{ github.actor }} `
            -Password ${{ secrets.GITHUB_TOKEN }} `
            -StorePasswordInClearText `
            -NonInteractive

As you can tell, this is super verbose and requires 2 actions to be "idempotent" since there is no upsert operator for sources with nuget.exe, so we "try to remove" (ignore failures) and then "add".

We will move this into a composite action to reduce noise in our main workflow, but it would be much nicer if it was possible to specify the source directly on the nuget/setup-nuget action itself, as additional parameters.