Create release pipeline for MRTK3

[AMollis]

This issue has been migrated a new MRTK repository, and the status of this issue will now be tracked at the following location:

• Create release pipeline for MRTK3 MixedRealityToolkit/MixedRealityToolkit-Unity#112

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• Setup new pipeline to create release candidate package. Publish to internal feed
• Update pack-upm.ps1 script to download release candidate package and then reversion, rename, and repackage it.

Preview Packages

CI Builds =  [Major].[Minor].[Patch]-build.pre.[PreviewNumber].[DateNumber].[Counter]    (counter based off "DateNumber")
Release Candidate  = [Major].[Minor].[Patch]-prerelease.pre.[PreviewNumber].[DateNumber].[Counter]   (counter based off "DateNumber")
Release = [Major].[Minor].[Patch]-pre.[PreviewNumber]  

3.0.2-build.pre.15.yyyyMMdd.2

Non-Preview Packages

CI Builds =  [Major].[Minor].[Patch]-build.[DateNumber].[Counter]    (counter based off "DateNumber")
Release Candidate  = [Major].[Minor].[Patch]-prerelease.[DateNumber].[Counter]   (counter based off "DateNumber")
Release = [Major].[Minor].[Patch]

3.0.2-build.yyyyMMdd.2

[AMollis]

Work has been completed