Materials: Linked object needs Material and Appearance overrides

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Problem description

There are a few issues with linked objects that are related.

There is a property "Override Materials" that previously referred to appearances. This needs to be split in two.

Currently there is no way to do this override other than the hard coded values. This needs to use "Set Material..." and "Set Appearance..." as for regular objects, but only when the overrides are enabled.

### Full version info

```shell
OS: Windows 11 build 26100
Architecture: x86_64
Version: 1.1.0dev.39861 (Git)
Build type: Release
Branch: main
Hash: 4cb01753ed532263dddae60e40e8641df56f9185
Python 3.12.4, Qt 6.7.2, Coin 4.0.2, Vtk 9.3.0, OCC 7.8.0
Locale: English/Canada (en_CA)
Stylesheet/Theme/QtStyle: unset/FreeCAD Classic/windows11
Installed mods:
* CfdOF 1.27.10
* ExplodedAssembly
* MaterialDB 0.0.1
* OpenTheme 2024.9.1
* Rocket 4.1.1
* sheetmetal 0.6.13
```

### Subproject(s) affected?

None

### Anything else?

_No response_

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct