Contextual top bar when drawing

[quincylvania]

This issue is strongly related to #5882, which should be done before or with this.

The existing top bar is relatively static no matter what mode the user is in. While drawing an area it looks like this:

There are several buttons we can remove during drawing to free up space:

• Remove the Save button. There's no need to upload in the middle of drawing.
• Remove the buttons for the other drawing modes. We disable clicking on them anyway during drawing.

With the extra space we can add UI elements specific to drawing:

• A Cancel or Done button to exit the mode. This would benefit everyone, but especially touchscreen users who currently have no great way to finish drawing.
• Instructions for drawing the geometry type. After Allow choosing the feature type before drawing #5882 this can also be specific to the preset.
• A toggle for line/orthogonal/arc drawing. Finally, a home for Orthogonal / Building drawing tool #2699. Ideally these would work for both lines and areas you could switch segment types in the middle of drawing a way.
• A control for locking/unlocking the draw mode (see Allow locking of the draw mode #5874).
• After Allow choosing the feature type before drawing #5882 we could even consider controls specific to the feature type. Like toggling between adding poles or towers when drawing power lines (see Mapping power lines #5701).