The MSPT metric impact performances with ticks above 50ms

[WarnDa]

Describe the issue

I had some mspt above 50 so I did a spark with tick>50ms and saw that PLAN is one of my three plugins that is reported.

Exceptions & Other Logs

I'm fixing the two other plugin currently, but maybe plan can be fixed too !
Here is the spark :
https://spark.lucko.me/SlRnnoLv9R

Plugin versions

Plan version 5.7 build 3158

Additional information

Using this dev build : #4243
I'm on a fork of paper

[AuroraLS3]

Impact: 8ms once per second due to reflection

Solution: cache MinecraftServer class and MinecraftServer instance