UI: Use signal vector for status bar

[cg2121]

Description

The stream output signals are now put inside of a vector.

Motivation and Context

Less code

How Has This Been Tested?

Disconnected and reconnected stream

Types of changes

• Code cleanup (non-breaking change which makes code smaller or more readable)

Checklist:

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

[PatTheMav]

I guess this change relies on the deallocators of the signals being called when the vector is cleared (which it does).

In general I'm not in favour of relying on deallocators in C++ (because C++ is a mess) versus calling cleanup code explicitly, but it's the way OBSSignal is designed.