5259: reintroduce shotgun bug r=def- a=C0D3D3V
fixes#5258
bug got fixed by the math changes in 68bcd21eff
This fix introduces a hard coded velocity that the player would get like before. (It could be that this has slightly other behaviour, because before the produced NaN values where converted to ints in CCharacterCore::Quantize (so some other logic may be confronted with the NaN values before), but it should most likely not be noticeable because it is fast enough)
We could now make this bug optional, by adding it to our mapbugs, or adding a server setting for it.
## Checklist
- [x] Tested the change ingame
- [ ] Provided screenshots if it is a visual change
- [ ] Tested in combination with possibly related configuration options
- [ ] Written a unit test if it works standalone, system.c especially
- [x] Considered possible null pointers and out of bounds array indexing
- [x] Changed no physics that affect existing maps
- [x] Tested the change with [ASan+UBSan or valgrind's memcheck](https://github.com/ddnet/ddnet/#using-addresssanitizer--undefinedbehavioursanitizer-or-valgrinds-memcheck) (optional)
Co-authored-by: c0d3d3v <c0d3d3v@mag-keinen-spam.de>
ce9b16d6f6