Add size control for normal rendering mode

[mwestphal]

Is your feature request related to a problem? Please describe.
F3D recently added support for normal rendering (#2958) however when viewed from a distance the arrow field is very dense making it hard to understand anything.
Zooming in fixes the issue but being able to control the size of the arrows would probably be helpful for users that want to see their whole data.

Describe the solution you'd like

• Add a CLI/libf3d option to control the the size of the normal arrows
• Add tests
• Add doc
• Consider making the default value not 1 but a slightly lower value and update baselines accordingly (to be discussed)

[Ryon-Tom]

Hello could I have this issue?

[mwestphal]

Assigned :)