Separate CCVars into separate files

[Simyon264]

About the PR

This PR separates the CCVars file into a partial class with multiple files in order to make them actually readable. This will make adding new CVars much easier.

Technical details

moved stuff

Requirements

• I have read and am following the Pull Request and Changelog Guidelines.
• I have added media to this PR or it does not require an ingame showcase.

Breaking changes

The file CCVars was split up into many tiny files. Downstreams are encouraged to create a new CVar class for their own fork in order to avoid merge conflicts as such:

namespace Content.Shared.MyAwesomeFork.CCVar;

[CVarDefs]
public sealed partial class MyAwesomeForkCCVars : CVars
{
    /// <summary>
    /// If true, makes people sell their souls on connection.
    /// </summary>
    public static readonly CVarDef<bool> GameAwesomeForkSellSoulOnJoin =
        CVarDef.Create("game.awesome_fork.sell_soul_on_join", true, CVar.SERVERONLY);
}

[TheShuEd]

Its really helpful for forks and ccvar management

[VasilisThePikachu]

Before merging mind if you make a PR to update the hosting docs (or really any doc pointing to ccvars)

I can also do this but I'm not promising anything so it may be faster for you to do docs pr as well.

[Simyon264]

space-wizards/docs#345