Properly unload plugins from all places in latest paper

[DasBabyPixel]

Just thought I'd make this PR in case anyone is interested. Fixes some memory leaks which cause plugins to not be unloaded correctly. I have only tested this with paper 1.21.1, not older versions / other server implementations

[Test-Account666]

Thank you for this. I'll have a look and test it against some versions.

And sorry for not being very active at the moment

[codeHusky]

@Test-Account666 Any plan to still merge this in?

[Test-Account666]

I haven't forgotten about this PR, don't worry.

I plan to merge it alongside deprecating older versions.

I'd like to move on from ancient versions like 1.8

[codeHusky]

This PR has an incompatibility issue with Folia, this change seems to fix it though I'm unsure if the Folia code behaves the same

[Test-Account666]

Oh, yeah. Makes sense.

Thanks for the reminder about Folia