mac-capture: Add SCStreamDelegate to stream to log capture errors

[gxalpha]

Description

Adds a SCStreamDelegate logging when SCK sources stop with an error.

Motivation and Context

Having a delegate is needed for a future PR where we have to introduce some sort of UI feature that re-enables a stopped stream, as macOS 14 adds a UI for the user to stop SCK streams outside of OBS, or for when the computer goes to sleep (see #8928).
I'm also low-key hoping (at least a tiny bit) that it could help us diagnose remaining freezing issues that still pop up very sporadically (assuming that they exit with error codes), and as such wouldn't mind this change making its way into a hotfix release (assuming other people think that's acceptable).

How Has This Been Tested?

macOS 14
Put computer to sleep and (when waking it up again) saw the "Stream stopped with no capture source" message in the log.
Stopped the stream via the menu bar and saw the "User stopped stream" message.

Types of changes

• Tweak (non-breaking change to improve existing functionality)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.