improve lag compensated hitreg

[wuangg]

Description

Improves lag compensated hit registration, to make sure it is compatible with modification from Bukkit event calls when registering movement.

• Fixes #350
• LagCompensator#registerMovement now is compatible with modification from Bukkit event calls (more detail in code comments).

How has this been tested?

This PR should be tested more properly, even though #350 has been fixed by testing with latest version of Citizens2. I'm not sure if it should work with other plugins use Citizens2 as dependency.

Checklist:

• [x] I have reviewed my code thoroughly.
• [x] I have tested my code.
• [x] My changes generate no new warnings

[Sculas]

Thanks a lot for this PR! Also, thanks @Elierrr for the ping :)

I'll merge this for now (so we can get a CI build) and then ask @refractored or someone else in the Discord to test it out, as I'm currently not available to help out on this.