Timeslice level names are no longer configurable [BUG]

[tsmbland]

Describe the bug

Previously you could choose the name of the timeslice levels using the level_names argument in settings.toml. However, since #289, the default level names ("month", "day" and "hour") are hardcoded in many different places in the code, but we still accept the level_names argument in settings.toml. If anyone tries to change this, the model will fail.

I think before it would also accept fewer or more timeslice levels (at least according to the documentation, although I haven't tried this), but obviously now it's restricted to three levels.

To Reproduce

Try changing level_names for any of the example models

Expected behavior

We should either change the code to stop hardcoding level names, or remove the level_names option from settings.toml so the defaults ("month", "day" and "hour") are mandated.

I'd probably go with the latter, as it doesn't seem like there would be much use for changing the level names, but maybe I'm wrong?

Screenshots

If applicable, add screenshots to help explain your problem.

Context

Please, complete the following to better understand the system you are using to run MUSE.

• Operating system (eg. Windows 10):
• MUSE version (eg. 1.0.1):
• Installation method (eg. pipx, pip, development mode):
• Python version (you can get this running python --version):