fix(containment): allow shared network exits

[arazmj]

Description

Allow units stored in a shared tunnel or cave network to exit through another
endpoint controlled by the same player.

The non-retail containment guard required the requested exit object to be the
unit's exact containedBy object. Tunnel passengers are stored by the shared
network, so valid exit commands through a different tunnel returned before
containment logic could process them.

Changes

• recognize tunnel and cave containment capabilities
• permit exits between same-player endpoints of the same shared container type
• continue rejecting unrelated containers and enemy-controlled endpoints
• apply the fix to Zero Hour and Generals

Validation

• built Zero Hour and Generals successfully with the macOS Vulkan preset
• traced the shared input path through the inventory control bar and game-logic
  dispatch to both containment exit functions
• verified the guard remains strict for ordinary non-network containers

[arazmj]

Additional real-world validation: completed another multiplayer game with two macOS GeneralsX clients and one deterministic Windows client. Map loading, shared tunnel exits, sound, and synchronization all remained working with no reported problems.

[fbraz3]

Could you please resolve the conflicts? thanks!

[arazmj]

Resolved: the branch is rebased onto current main, conflicts are fixed, and the PR is mergeable. I also tightened the shared-network check based on cave-network review feedback: both endpoints must now expose the same non-null shared contained-items list, so distinct CaveIndex/TunnelTracker networks remain isolated. Current CI is fully green for Linux/macOS builds and replays.

[Caball009]

A little later but TSH fixed this as well: https://github.com/TheSuperHackers/GeneralsGameCode/pull/3136/changes