Revert "Build the Splunk package from its NUSPEC rather than the CSPROJ"

This reverts commit 044c7be0bcfcbc1de3c8e713af91ec2b3a619fa1.
Revert "Revert "Build the Splunk package from its NUSPEC rather than the CSPROJ""

This reverts commit 9dc70e22f9663491c5b478730f27e98038137f69.
Revert "Revert "Revert "Build the Splunk package from its NUSPEC rather than the CSPROJ"""

This reverts commit 38867dedc63d089218d04d2f7836070f6e1ca7c0.