ATLauncher: Handle depends for main class and extra arguments

[jamierocks]

Closes #485

This fixes a bug with installing All The Forge 8 where the main class would erronously be set to LaunchWrapper.

This was a result of not handling depends on mainClass (see below for an example). Where the mod depended on was no longer present (mod loaders have much better support on ATLauncher now).

    "mainClass": {
        "mainClass": "net.minecraft.launchwrapper.Launch",
        "depends": "Minecraft Forge"
    },

---

The commit(s) contained within this pull request have been cherry-picked from my own private fork of MultiMC from circa September 2021.

For the benefit of PolyMC: My fork is prior to multiple licences covering the MultiMC codebase, and no longer pulls changes from MultiMC as a result of these developments.

For the benefit of PolyMC and MultiMC: I only do development on a PolyMC or MultiMC workspace to resolve merge-conflicts, and to get changes building. No commits are ever cherry-picked onto my fork from a PolyMC or MultiMC workspace - nor between the two in either direction.

[Scrumplex]

Thanks

[Scrumplex]

We had someone with this problem once. I assumed it was a bug with the pack, but apparently it wasnt :D

[jamierocks]

I've added an additional patch to fix installing SevTech: Ages :)

[flowln]

👌