frontend: Make OBSAbout self contained

[cg2121]

Description

This makes it so OBSAbout isn't tangled with OBSBasic.

Motivation and Context

Make frontend less messy

How Has This Been Tested?

Opened about dialog to make sure it still worked

Types of changes

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

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.

[PatTheMav]

So this encapsulates the management (and updating) of the patronJSON entirely into the OBSAbout class? Nice.

Why does it need to include OBSApp though?

[cg2121]

It is needed for the GetDataFilePath function. OBSApp.hpp was included with OBSBasic.hpp before.

[RytoEX]

This has a merge conflict. cc @Warchamp7

[Warchamp7]

This has a merge conflict. cc @Warchamp7

Rebased

[Warchamp7]

Now featuring 100% less accidental submodule commits.

[RytoEX]

Might have a conflict with #12934 since that changes some stuff regarding RemoteTextThread.

[RytoEX]

Now that #12934 is merged, please resolve merge conflicts and ensure that this still functions as intended after changes to RemoteTextThread.

[cg2121]

I fixed the merge conflicts and made sure it still works with the changes to the RemoteTextThread.

[PatTheMav]

I've encountered the issue of the about dialog opening up but the patron list was empty once, but haven't been able to reproduce it yet. In all consecutive attempts it worked as it should, though it's a bit unfortunate that a user can trigger the presentation of the dialog, but then potentially nothing will happen until eventually the remote text thread returns either an error message or the patron list.

IMO the dialog should not appear conditionally (because the user triggered a menu action, so the dialog should appear immediately) and instead should be able to handle an empty patron list gracefully, though that'd be out of scope for this PR.