[Feature Request] TechDraw: Box Selection for TechDraw lines

### Is there an existing request for this?

- [X] I have searched the existing requests

### Forums discussion

https://forum.freecadweb.org/viewtopic.php?f=35&t=69436

### Subproject(s) affected?

Techdraw

### Idea description

Add a way to use box selection to select individual lines in a Techdraw view, so they can, for example, have their display options using `TechDraw_DecorateLine`.

This is specially useful for cases when the 3D part comes from a STEP file that includes large amounts of geometry, that ends up as large amounts of lines, as each operation will take a noticeable amount of time, and you may want to select a large number of very small lines.

### Anything else?

_No response_

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct