Fix problems with operator keymap function

Fix problems with operator keymap function

1. Introduce using-show-keymap and using-show-operator-keymap vars to
make it clear how we are entering which-key

2. Add inhibit-next-operator-keymap for keys in the operator maps that
are bound to commands that read the next key "manually"

3. Fix problem where the next page hint was only being shown sometimes
in the operator maps. Need to distinguish between show-operator-keymap
and the possibility that an operator is active but the usual which-key
popup is showing.