Add new menu layouts

[orhun]

Is your feature request related to a problem? Please describe.
It would be nice to have different menu layouts instead of having only one which is fixed. We already have the functionality for changing the block sizes and moving them around. This new menu(s) could be possibly change the overall layout for different use cases such as:

• Kernel monitoring (dmesg) mode where the "Kernel Activities" block is maximized.
• Inspection mode where only the module info is shown.

And a couple of other scenarios...

Describe the solution you'd like
Define a list of menu layouts and add a key binding for changing the current layout.

Describe alternatives you've considered
There could be a command-line argument for launching kmon with the given menu type. e.g. kmon --menu activities

Additional context
bpytop has something similar where you press m and the layout changes.