bug: apply a plugin's configuration on community servers

[lukepolo]

A plugin's configuration only ever ran as part of a match, so community dedicated servers (no match) ran plugins on their defaults — e.g. the Inventory Simulator kept invsim_url pointing at inventory.cstrike.app.

• Community servers now write each loaded plugin's cvars into cfg/gamemode_<valve mode>_server.cfg, which CS2 execs on every map load
• Plugin cvars run before the game mode's, so the mode wins a conflict, same order as a match
• Ranked and Practice servers are skipped; their matches already exec the plugin layers
• Editing a plugin's configuration still needs a server restart to reach running servers