Plot: Option to lock (sync) x and y axis scale

[ljburtz]

plot setting to lock the x and y axis scales (aspect ratio) -> Important for "map" type applications (when chossing the x axis is "msg path (accumulated)" for example a square robot trajectory should be a square/not a rectangle!

~feature 2. fix xmin and xmax as well as ymin and ymax (important for consistent/comparable plots)~ [ @amacneil edit: moved to #3991 ]

simple additional settings in the 'plot panel settings' would address this

[amacneil]

@ljburtz let's keep each feature request in a separate ticket. I split the xmin/xmax request into https://github.com/foxglove/studio/issues/3991