Fix V4L2 nonui apply

[GrantAbell]

Description

This is a patch which forces v4l2 camera property changes to always use VIDEOC_S_CTRL to make writes to V4L2 devices.

What this patch changes:

• Adds a reusable v4l2_apply_controls() helper in v4l2-controls.c.
• Enumerates valid controls, pulls desired values from OBS settings, compares against current device values with VIDIOC_G_CTRL, and only writes with VIDIOC_S_CTRL when needed.
• Calls that helper from v4l2_update() so startup, websocket, Move, and any other non-UI setting updates all go through a real device apply step.

Motivation and Context

• I kept running into issues where only the built in Camera Properties GUI for my OBS V4L2 source would apply changes, while websocket and plugins would not.

How Has This Been Tested?

• Patched locally against flatpak upstream
• OBS opens without error
• WebSocket calls to adjust V4L2 camera property via SetInputSettings now works, whereas before it did not.
• Manual UI updates still work

Types of changes

• Bug fix (non-breaking change which fixes an issue)

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.