Add a SlimefunItem constructor that only needs ItemGroup and SlimefunItemStack

[ProfElements]

Description

I have a seperate system of managing recipes and would like a shorthand to not have to define them at item creation time.

Proposed changes

Add a SlimefunItem constructor that just passed RecipeType.NULL and empty recipe for its recipe and input fields.

Related Issues (if applicable)

Checklist

• I have fully tested the proposed changes and promise that they will not break everything into chaos.
• I have also tested the proposed changes in combination with various popular addons and can confirm my changes do not break them.
• I have made sure that the proposed changes do not break compatibility across the supported Minecraft versions (1.16.* - 1.20.*).
• I followed the existing code standards and didn't mess up the formatting.
• I did my best to add documentation to any public classes or methods I added.
• I have added Nonnull and Nullable annotations to my methods to indicate their behaviour for null values
• I added sufficient Unit Tests to cover my code.

[github-actions]

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feature/**	🎈 Feature
fix/**	✨ Fix
chore/**	🧹 Chores
api/**	🔧 API
performance/**	💡 Performance Optimization
compatibility/**	🤝 Compatibility

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[github-actions]

Slimefun preview build

A Slimefun preview build is available for testing!
Commit: 8430677f

https://preview-builds.walshy.dev/download/Slimefun/4179/8430677f

Note: This is not a supported build and is only here for the purposes of testing.
Do not run this on a live server and do not report bugs anywhere but this PR!

[JustAHuman-xD]

LGTM, don't see a reason not to

[TheBusyBiscuit]

LGTM