Pin Xcode 16

[mbg]

Risk assessment

For internal use only. Please select the risk level of this change:

• Low risk: Changes are fully under feature flags, or have been fully tested and validated in pre-production environments and are highly observable, or are documentation or test only.

Merge / deployment checklist

• Confirm this change is backwards compatible with existing workflows.
• Consider adding a changelog entry for this change.
• Confirm the readme and docs have been updated if necessary.

[Copilot]

Pull Request Overview

This PR pins the CodeQL Action's Swift-related tests to use Xcode 16 specifically on macOS runners. The change removes the previous Swift setup action and replaces it with a direct Xcode version selection approach.

Key changes:

• Adds Xcode 16 selection step to all Swift-related test workflows
• Removes the custom Swift setup action that was previously used
• Ensures consistent Xcode version across all Swift testing environments

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
pr-checks/checks/swift-custom-build.yml	Adds Xcode 16 pinning and removes Swift setup action
pr-checks/checks/swift-autobuild.yml	Adds Xcode 16 pinning and removes Swift setup action
pr-checks/checks/multi-language-autodetect.yml	Adds Xcode 16 pinning and removes Swift setup action
pr-checks/checks/export-file-baseline-information.yml	Adds Xcode 16 pinning and removes Swift setup action
.github/workflows/__swift-custom-build.yml	Generated workflow file reflecting the Swift test changes
.github/workflows/__swift-autobuild.yml	Generated workflow file reflecting the Swift test changes
.github/workflows/__multi-language-autodetect.yml	Generated workflow file reflecting the Swift test changes
.github/workflows/__export-file-baseline-information.yml	Generated workflow file reflecting the Swift test changes
.github/actions/setup-swift/action.yml	Removes the entire Swift setup action as it's no longer needed

[mbg]

@redsun82 I have removed the pinning step from the two workflows that only use nightly-latest and added an extra condition on the step for the other two workflows so that it doesn't run when matrix.version == 'nightly-latest'.