#2255: Extract MSI build logic into shell script

[Caylipp]

This PR fixes #2255

No macOS PKG build exists in the current workflows, so this PR only extracts the Windows MSI build.

Implemented changes:

• Add windows-installer/build-msi.sh
• Replace the inline MSI build logic in nightly-build.yml
• Replace the inline MSI build logic in release.yml
• Keep the workflows focused on orchestration

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Testing instructions

Please add conscise, understandable instructions on how a reviewer can test/verify the functionality of your contribution here:

1. Validated the shell script syntax with:
   bash -n windows-installer/build-msi.sh

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