obs-text: Render only when changed

[exeldro]

Description

Render text only when changed

Motivation and Context

Rendering text can take lots of time (in my testing example 86 ms), so in case nothing changed, like for example a obs-websocket request to update the text to the same value, the rendering step can be skipped.

How Has This Been Tested?

On windows 11 by changing a text file without resulting text changes to be rendered and by calling SetInputSettings on obs-websockets

Types of changes

• Performance enhancement (non-breaking change which improves efficiency)

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.