TextureStorage::texture_debug_usage and MeshStorage::mesh_debug_usage are not thread-safe

### Tested versions

- current master @ 3c9d03b8755968ae305b8cfebe886c56402cb044

### System information

macOS Sequoia (15.6.0) - Multi-window, 1 monitor - Metal (Forward+) - integrated Apple M4 Max (Apple9) - Apple M4 Max (16 threads)

### Issue description

texture_debug_usage and mesh_debug_usage are not thread-safe. While `get_owned_list()` is thread-safe, iterating through the list is not. The mutex is not held while iterating through the list, which means that textures/meshes can be freed during iteration, which can lead to a segfault when de-referencing them while populating the info objects.

This can be likely be fixed by just locking the mutex before iterating through the list.

### Steps to reproduce

1. constantly call either function on a task thread while loading and unloading scenes on the main thread
2. Eventually, you'll get a segfault.

### Minimal reproduction project (MRP)

N/A

Start by locating TextureStorage::texture_debug_usage and MeshStorage::mesh_debug_usage, then read how get_owned_list() and its returned lists are used during iteration. Reproduce the concurrent task-thread calls while loading and unloading scenes, and verify both functions remain safe without segfaults during that workload.

Written by the indexing model from the issue text.