Previously the default values were left non-zero to avoid having to
update scripts. However, this meant it wasn't possible to setup
non-modal key bindings for smooth & randomize.
Now these operators follow logic of many other operators where setting
the value executes immediately, leaving unset runs modal.
Existing keymaps & scripts will need to be updated.
Addresses issue raised in f4a4ec8425.
Previously these used a gizmo to redo the operator however this
complicated having on-screen gizmos to access tools (see T66304).
Replace this with a generic way to make an operator that only has an
execute function into a modal operator.
This is used for smooth and randomize tools.
Unlike operator gestures, this handles storing and resetting the data.
Currently this only handles edit-mode data, however it's can be
extended to other kinds of data.
