Update release script to download server sdk and package it alongside the tarball

[AWSJackson]

With 2.x, we changed up the artifact we released from the tarball to a ZIP including the tarball, the CSharp Server SDK for Unity (with the license file removed), and a readme for installation instructions. This PR looks to update the scripts to handle this new artifact automatically.

Update release script to,

• Accept a parameter for the server sdk version for the release
• Download the server sdk, remove the license file, and re-package the zip
• Package a zip including an installation readme, the server sdk zip, and the plugin tarball
• Use $LASTEXITCODE to accurately stop execution of the script when an error occurs (at any level)
  • Known issue: If the error occurs with the call command itself (ex: & "$PSScriptRoot\build.ps1"), $LASTEXITCODE will not be set and the script won't terminate.
• Prevent npm pack from including new artifact files (repeated calls to export.ps1 would exponentially grow the tarball size)
• Add some color to the logs:
  • Green - Important step succeeded (building the sample project and packaging the release zip)
  • Yellow - Other step succeeded (clean up, intermediate build steps, etc.)
  • DarkYellow - Informational logs (identified plugin version, where to find sample project build logs)
  • Red - Most errors that occur
  • DarkRed - Important step failed (building the sample project)

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