Replace implicit lamda captures for C++20

[RytoEX]

Description

Implicit capture of 'this' with a capture default of '=' is deprecated in C++20. While the standard recommends replacing '=' with '=, this', that syntax is not C++17 compatible, and we will likely need some transition period where obs-studio and its modules are still built using C++17.

Motivation and Context

Want obs-studio and its submodules to build with C++20 some day.

How Has This Been Tested?

Compiled and tested on Windows 11.

Types of changes

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

Checklist:

• I have read the contributing document.
• My code has been run through clang-format.
• My code follows the project's style guidelines
• My code is not on the master branch.
• My code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

[PatTheMav]

My initial reaction is that "explicit capture lists" are actually great (explicit is better than implicit), though too long lists might become harder to parse.

I think in that case the same applies as with function signatures: If you design it in such a way that it requires ~10 arguments, chances are that those arguments might be better placed in a structure and that structure being passed along as the argument (or context data).