cmake: Update CMake files for build system 3.0 update

[PatTheMav]

Description

This PR updates the CMake build files to be compatible with the build system 3.0 update on the main repository.

Motivation and Context

This PR attempts to retain the possibility to generate a build project standalone but also support new functionality introduced by the build system 3.0 update:

• The current build script is retained as the "legacy" script (which will still be used to generate build projects on Linux and macOS)
• The new build script is used for macOS builds by default at first

More information shall be available in the pull request on the main repository.

Note: This PR needs to be merged first, then the associated commit hash updated for the obs-websocket submodule at obs-studio.

How Has This Been Tested?

• New build scripts were tested as part of the overall update on macOS 13, Ubuntu 22.10, and Windows 11.

Types of changes

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

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 master or a release/* branch.
• [x] The code has been tested.
• [x] I have included updates to all appropriate documentation.