Effect/instrument window positions are not saved

### System Information

Arch Linux, GNOME

### LMMS Version(s)

master

### Most Recent Working Version

_No response_

### Bug Summary

If you open any instrument/effect control windows, move them around, and then save the project, when you reopen the project the effect windows will all be closed. And when you go to reopen them, they do not appear in the same place.

This is in contrast to the default windows, such as the Song Editor or the Piano Roll, which keep their position between sessions.

### Expected Behaviour

When saving a project, the position and visibility of all windows should be saved.

### Steps To Reproduce

1. Create a new project
2. Add an effect/instrument
3. Open the effect/instrument's controls window
4. Move it around, and save the project
5. Reopen the saved project
6. The window is not visible, and not in the same place.

### Logs

### Screenshots / Minimum Reproducible Project

_No response_

### Please search the issue tracker for existing bug reports before submitting your own.

- [x] I have searched all existing issues and confirmed that this is not a duplicate.

Start by reproducing the issue with an instrument or effect control window, then trace how project saving and reopening handle the existing Song Editor or Piano Roll window state. Compare those paths with instrument/effect windows. Done means their visibility and positions persist after reopening a saved project, verified using the listed reproduction steps.

Written by the indexing model from the issue text.