fix: emit 'shutdown' outside -[NSApplication terminate:]

[codebytere]

Description of Change

Closes #24105.

When macOS shuts down, Cocoa will send an NSWorkspaceWillPowerOffNotification followed by -[NSApplication terminate:]. The original PR that added this on macOS hooked into the latter instead of the former, thereby creating the side effect that it would also be called when the app itself terminated.

For more effective dx, this PR registers for NSWorkspaceWillPowerOffNotification and then emits 'shutdown' when the notification is sent instead.

cc @zcbenz @deepak1556 @nornagon

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• PR title follows semantic commit guidelines
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.
• This is NOT A BREAKING CHANGE. Breaking changes may not be merged to master until 11-x-y is branched.

Release Notes

Notes: Fixed an issue where shutdown would be emitted both on app and system shutdown on macOS.

[release-clerk]

Release Notes Persisted

Fixed an issue where shutdown would be emitted both on app and system shutdown on macOS.

[trop]

I have automatically backported this PR to "10-x-y", please check out #24139

[trop]

I have automatically backported this PR to "8-x-y", please check out #24140

[trop]

I have automatically backported this PR to "9-x-y", please check out #24141