Isolate server config files from Shulker init scripts in ConfigMaps

[jeremylvln]

trafficstars

I may have attempted to utilize this feature incorrectly. But it sounds like it's meant to allow for the overriding of the config map that provides the proxy config (velocity-config.toml as defined in the Shulker provided configmap). But in actual usage, it appears that it wants theinit-fs.sh file to be defined in the config map, also likely other files like the probe-readiness.sh. I'm not sure if this is the intended behaviour to allow for the overriding of the init-fs.sh.

Originally posted by @TehNeon in https://github.com/jeremylvln/Shulker/issues/447#issuecomment-2017077012