Upgrade Catch2 library to v2.13.8

Older version was [problematic](catchorg/Catch2#2272) during C++20 migration so I updated library version. Decided to make it different PR because C++20 migration appears to be not so easy as I thought so I decided to split away complete parts.

I just copied their file from [their release](https://github.com/catchorg/Catch2/releases/tag/v2.13.8) in github.
I edited one variable name in their code because it clashed with our translation define (changed it from `_` to `__`).