Better subtitle handling

[massimilianodelliubaldini]

The current method for subtitle handling is to move a vertex shader based on the presence of a certain index buffer. This leads to some oddities, like the left side of the screen "popping" into/out of a mission rather than fading in/out. There's a few other visual oddities as pointed out by @martinsstuff in #6. I think he also wrote the original implementation of it, IIRC.

This issue is to see if there's a better method for moving the subtitles in game.

[WinkelCode]

(I already mentioned in Discord but I'll post it here again for the record, I also did indeed write the original "implementation"/workaround)

My idea was to potentially use a Regex pattern or something else to determine the position of the actual text (the properly centered cutscene subtitles/the shifted in-game conversation text) and act based on that directly instead of using the presence of some unrelated shader or index buffer.

Besides that it is worth some investigation if there isn't some way to individually modify only the in-game conversation text, I am not entirely convinced that we can only move both subtitle variants and the fading black box together.