Move vendor/lua to a submodule

[Pirulax]

I made a PR in which Qais suggested me to use create a repo for our Lua vendor, and do modifications there instead.
This PR implements his idea.
It contains all previous commits back to 2008.

TODO: Test if everything works.

[Pirulax]

Thanks man.. I was getting very annoyed.

[Pirulax]

Discussion over at Discord.

[Pirulax]

I'll need to rebase this if we decide to merge it

[patrikjuvonen]

Let's not do this for Lua at this time.

[Pirulax]

Let's do it now, what do you think?
We need submodules for Luau anyways.

[TheNormalnij]

There is no benefits from this.
Submodules are good for external dependencies. For internal dependencies they make life harder.
Lua submodule just adds extra step in development:

1. Create PR into lua repo
2. Create PR into mta-blue remove with submodule update

This has no sense. Submodules should be used for external or shared dependencies

[tederis]

I would agree with TheNormalnij. The Lua version MTA uses is the internal thing. It is an inseparatable part of MTA that cannot be used in anywhere else.