Add Commons system for shared inventories between grid objects

[daveey]

TL;DR

Added a Commons system to MettaGrid that allows multiple grid objects to share a common inventory.

What changed?

• Added Commons and CommonsConfig classes to implement shared inventories
• Extended GridObject with methods to associate objects with a commons
• Updated MettaGrid to initialize commons from config and associate objects via tags
• Added support for specifying commons in Python configuration
• Objects can be associated with a commons via a tag (commons:name) or directly in config
• Added comprehensive tests for the commons functionality

How to test?

1. Create a commons configuration:

CommonsConfig(
    name="team_storage",
    inventory=InventoryConfig(
        initial={"gold": 100},
        limits={"resources": ResourceLimitsConfig(limit=1000, resources=["gold"])}
    )
)

2. Associate objects with the commons:

ChestConfig(name="team_chest", commons="team_storage")

3. Access the shared inventory through any associated object

4. Run the test suite:

python -m mettagrid.tests.test_commons

Why make this change?

This change enables shared resource management between multiple grid objects, which is useful for:

• Team-based resource sharing
• Creating common resource pools for groups of objects
• Implementing economic systems with shared inventories
• Supporting collaborative gameplay mechanics where multiple agents can contribute to and withdraw from a common resource pool

[daveey]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• Add observer_agent_id parameter to obs_features for agent-specific observations #4539
• Add Area of Effect (AOE) resource effects to grid objects #4538
• Add CommonsChest for shared inventory access across agents #4537
• Add Commons system for shared inventories between grid objects #4536 👈 (View in Graphite)
• Rename cog_arena.py to cogsguard.py and remove unused imports #4477
• Enhance attack system with armor, weapons, and configurable loot #4313 : 1 other dependent PR (#4321 )
• Make Transfer action optional and add vibe-triggered attack #4315
• Implement bidirectional resource transfer system with vibe-based triggers #4314
• Replace number_of_vibes with explicit vibes list in change_vibe action config #4489
• Refactor inventory system into dedicated InventoryConfig class #4356 : 2 other dependent PRs (#4328 , #4355 )
• Add ignore_limits parameter to inventory updates for initial setup #4360
• Rename test_performance to run_performance in mettagrid to avoid running in pytest #4370
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.