Update project structure with changes from obs-plugintemplate

[PatTheMav]

Description

Updates the build environment adapting the modernised plugin template. Includes updated build scripts for Windows, Linux, and macOS, as well as updated GitHub Actions workflow and action files.

The CMake scripts have been updated and use the updated plugin helper script as well, requiring the changes on obs-studio master branch (as OBS can be configured to do a library-only build which generates appropriate CMake packages).

Motivation and Context

Modernise project infrastructure to utilise benefits from updated obs-studio build system. Also brings the project a step closer to the unified obsproject build environment being in development.

How Has This Been Tested?

Plugin was built on CI for all main operating systems, codesigning and notarisation were tested for macOS with valid Apple Developer credentials.

Types of changes

Other Enhancement (anything not applicable to what is listed)

Checklist:

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

[tt2468]

Closing since the scope of the branch has changed