Fix server generating hash for all resource files on startup

[Pirulax]

Describe the bug
When the server starts up, it generates the hash for every resource file, even for resources that aren't loaded.
This process is very CPU and storage intensive, and when running the server on a HDD it takes ages. This is really annoying when debugging the server, where you need to stop and start the server a lot.

Expected behaviour
Only generate hashes when the resource is started. When stopped clear the hashes, and regenerate it all.

Version
Latest (1.5.8 something), doesn't matter.