toggle numpad always on is missing (was a previous feature)

**Problem**
In previous elementary versions (pre greeter update - aug 2019) there was an option to force the numpad to be always on (under Settings >> Options tab >> Miscellaneous compatibility options >> Default numeric keypad keys). That setting is no longer there.

https://elementaryos.stackexchange.com/questions/373/how-do-i-enable-numlock-at-login

For folks with apple keyboards (ie coming over to elementary) this is a little perplexing as there's actually no obvious key to make the numpad work (and in MacOS it has been 'always on'). So it is rather frustrating for us Mac users.

This is the case for Hera

**Suggestion**
Add an option under Settings>>Layout called 'Numpad behavior' .

Settings options:
1 - Default = Numeric keys;
2 - Off = Mouse cursor

What's the right default?
Of course we can argue which behavior is 'right for the default'. For Apple users this makes sense. Perhaps the default could be based on which keyboard the user chose so that default = numeric if any Apple keyboard chosen and default = cursor if other keyboard chosen?

If there's a big argument over this, I'd suggest just making it:
1 - Default = Mouse cursor;
2 - Numeric keys

**Workaround:**
I searched and found that actually the clear button is numlock on OSX

Apologies if this is actually tracked somewhere but I don't see it