Add fill and stroke color choices to the Pen tool options bar (#1188)

* Add basic layout - WIP

* Add color input min-width -> 80px

* First pass implementation - WIP

* Allow fill to be None

* Fix null Fill color

* refactor fill and stroke options into struct

* toolbar progress - WIP

* Switch is_working_color bool to PenColorType enum

* Add todo

* Add WorkingColorChanged event

* remove unused import

* Add WorkingColor[Primary/Secondary] icons

* Allow new strokes to have no color

* Set to base color when X is pressed (as per req)

* Improve icons for new UI layout design

* Add radio buttons

* Fix menu bar Edit12px -> Edit

* Add tooltips to radio buttons

* Make the color selector only on custom

* Fix edit icon correctly this time (whoops)

* Fix working colors icons

* Changes to improve the UX

* Remove lines obviated by Default::default()

* Make Eyedropper tool use working_color_changed event

* Fix tests

---------

Co-authored-by: Keavon Chambers <keavon@keavon.com>

frontend/assets/icon-16px-solid/edit.svg

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frontend/assets/icon-16px-solid/working-colors-primary.svg

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frontend/assets/icon-16px-solid/working-colors-secondary.svg

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+</svg>