[lua] hxcoro with -D lua-vanilla

[Simn]

I asked Claude to make hxcoro work in lua-vanilla mode and it turns out not much is needed: HaxeFoundation/hxcoro#175

With this I can indeed run its tests locally with lua 5.4 installed.

Obviously, I don't want to actually make the bitshift-related changes over there, so that's something we should look into here. The now adjustments also looks like something that could be adjusted over here.

[tobil4sk]

The bit part should be covered by #12599

[Simn]

We have removed the bit-op hacks after #12599 and things are working well! The rest of the hacks can hopefully be removed after #12865 and then we'll be fully vanilla.