Merged PR 248: Make observation flattening optional for agents.

## Summary
Same as other PR but this time we are merging into DEV.

The Proxy agent has a new config option, `flatten_obs`. If true, we use gymnasium flatten.

## Test process
Unit tests and inspection.

Related work items: #2143, #2154, #2161

src/primaite/config/_package_data/example_config.yaml

@@ -14,6 +14,8 @@ io_settings:
   save_checkpoints: true
   checkpoint_interval: 5
   save_step_metadata: false
+  save_pcap_logs: true
+  save_sys_logs: true
 
 
 game:
@@ -523,7 +525,7 @@ agents:
 
 
     agent_settings:
-      # ...
+      flatten_obs: true