Modpack bikeys are combined across server instances

[defy93]

Is your feature request related to a problem? Please describe. Problem were experiencing is with multiple arma instances, currently the backend creates all of its server instances in the same arma installation. This is a problem as all mod presets that are downloaded their bikeys are combined into the same arma 3 server keys folder, this allows players to join servers with a completely different preset by accident and inadvertently break things.

Describe the solution you'd like

• When creating a new server instance, we should be creating a new install directory.
• Bikeys should only be placed in the relevant instance folder that server is active on.

Describe alternatives you've considered

• My workaround for this currently is to run multiple docker containers of arma-server-manager forcing separate directories.

Additional context I am more than happy to PR this, however i'm not a Java expert (rather typescript, python & rust) if i get some time i may try and tackle this issue.