Backport project to support java 8

[Kaydax]

This not only fixes #11 but also allows MultiYggdrasil to support versions older than Minecraft 1.17.

This also adds shadowjar remapping of asm and gson, allowing it to work with forge and older versions without overlapping libraries. (Which normal authlib-injector does for asm)

Everything works the same as It currently does, but it just replaces code that uses the newer java versions with code that works with java 8

I also added in portable gradle for people who don't have a system install of it

I've tested this on:
Vanilla 1.20.4
Vanilla 1.12.2
Vanilla 1.8.9
Forge 1.12.2

I feel like thats a good amount of testing to make sure it works with both new and old versions

[YuxuanZuo]

Thank for your contribution! But unfortunately there may be a duplicate username problem on lower versions of Minecraft. I will merge this pr after completing the backward compatibility of the username distinction function