Remove Unirest and replace with Java's native HttpClient

[WalshyDev]

Description

When we first implemented Unirest, the goal was always to remove it once we moved to Java 11 minimum. It's been a while since this happened so let's do this.

This reduces the jar size from 4.7 MB (4782834 bytes) to 2.4 MB (2480486 bytes) so we remove ~2.3 MB.

Proposed changes

Removes Unirest with Java's native HttpClient (introduced in Java 11)

Related Issues (if applicable)

N/A

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]

Your Pull Request was automatically labelled as: "🧹 Chores"
Thank you for contributing to this project! ❤️

[github-actions]

Slimefun preview build

A Slimefun preview build is available for testing!
Commit: 296ce2b7

https://preview-builds.walshy.dev/download/Slimefun/4068/296ce2b7

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!

[J3fftw1]

please create unit tests

[WalshyDev]

This code cannot be unit tested, it's all private or ran as part of a task. Making it public doesn't make sense here

[sonarqubecloud]

Quality Gate passed

The SonarCloud Quality Gate passed, but some issues were introduced.

7 New issues
0 Security Hotspots
1.1% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud