We were re-implementing a few things order lines already support.
All we really needed was to not add a pp size label if one is provided.
Use `.hide_label()` in the mouse hover handler.
In an effort to simplify line creation and management from an order
mode here's a slew of changes:
- use our new ``LevelMarker`` for order lines and fully drop usage
of the original marker implementation stuff from `pg.InfiniteLine`
- add a left side label which shows the instrument's "units" value
- the most fundamental unit for the "size" of the order
- allow passing in an optional `marker_size: str` so that `action: str`
doesn't necessarily have to be passed (eg. when copying from an
existing line)
- change a couple of internal line config options to be public attrs
which can now be configured dynamically in real-time (since they're
all `bool` anyway):
* `hl_on_hover` -> `highlight_on_hover`
* `_always_show_labels` -> `always_show_labels`
- `LevelLine.set_level()` now only sets the position if it was **not**
called from the position changed signal (which would be redundant)
Tyler Goodlet