Pose/Transform query of TriangleMesh

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D/issues).
- [X] For Python issues, I have tested with the [latest development wheel](https://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](https://www.open3d.org/docs/release/) and the [latest documentation](https://www.open3d.org/docs/latest/) (for `main` branch).

### Proposed new feature or change

I think it's important and much more convenient for ppl to use, if TriangleMesh can offer a new function .pose() which will return the 4x4 homogeneous matrix represent its current pose. If this feature already exists somewhere that I didn't notice, please let me know. Otherwise, I think this is a very common function call appeared in other similar toolkit.

### References

_No response_

### Additional information

_No response_