[Ogre2] Destroying material is expensive and does not remove all textures

## Environment
* OS Version: 24.04
* Source or binary build?
source build, gz-rendering10

## Description
* Expected behavior: Destroying an Ogre2Material should be fast and it should clean up all unused textures created by the material, including diffuse, normal, roughness, metalness maps, lightmap, etc
* Actual behavior:
* The [Destroy()](https://github.com/gazebosim/gz-rendering/blob/fde53a65311c9eeeba73d68fbbe0689aa41332a5/ogre2/src/Ogre2Material.cc#L172) function can be quite expensive when there are many textures in the scene. The expensive part is that it [loops through all materials](https://github.com/gazebosim/gz-rendering/blob/fde53a65311c9eeeba73d68fbbe0689aa41332a5/ogre2/src/Ogre2Material.cc#L227) and checks to make sure they are not in use before removing them.
* In addition, it only [checks and cleans up the diffuse texture](https://github.com/gazebosim/gz-rendering/blob/fde53a65311c9eeeba73d68fbbe0689aa41332a5/ogre2/src/Ogre2Material.cc#L258) (`this->textureName`) and does not check for other texture maps like normal maps, etc. So other maps are not cleaned up properly.