Add a command line argument to rename/move config folder

[ghost]

Same as PaperMC/Paper#7948 and pufferfish-gg/Pufferfish#35

Add a --purpur-settings command-line argument to the startup flags so we are able to specify where purpur.yml is saved. For example --paper-settings-directory "settings/" saves all the paper configs to the settings/paper.yml folder within the server directory.

So it could be for example --purpur-settings "settings/purpur.yml"

I know you are currently working on implementing the new config system so not sure if this was thought of for implementation but it would be nice.

[BillyGalbreath]

https://github.com/PurpurMC/Purpur/blob/ver/1.19/patches/server/0004-Purpur-config-files.patch#L74-L82