Add release artifactbundle workflow

[hiryanbautista]

Summary

Adds release automation for publishing SwiftPackageListBinary as a SwiftPM binary artifact bundle.

This allows projects to add SwiftPackageList through Swift Package Manager while still referencing the swift-package-list executable from a custom build phase, without requiring the tool to be installed separately on every developer or CI machine.

References #171.

Changes

• Builds and uploads SwiftPackageListBinary.artifactbundle.zip during release publishing
• Reuses the executable already produced by the existing release build job
• Computes the SwiftPM checksum for the artifact bundle
• Updates Package.swift with a SwiftPackageListBinary binary target
• Supports the first release where the binary product/target does not exist yet, and later releases where only the URL/checksum need updating

Motivation

The build tool plugin is useful for common setups, but some projects need to invoke swift-package-list from a custom Run Script phase, especially when combining generated acknowledgements with an existing manually maintained Settings.bundle.

Providing a binary target lets those projects depend on the executable through SPM instead of relying on a machine-level installation.