Legacy handling of triple-screen setups messes with modern monitors

I've now run into two issues with FSO's handling of ultra-wide resolutions and people trying to play BPC.
[one on discord here](https://discord.com/channels/223511295431933953/1474247530165571725/1474247530165571725)
[And one on the forums here.](https://www.hard-light.net/forums/index.php?topic=98633.0)

Funnily enough, both of these cases involve a samsung odessey G9 monitor. This monitor has a display resolution of 5120x1440 for an aspect resolution of 32:9.

The workaround is to use the `-center_res` command, and simply type in the user's native resolution. Or a 16:9 resolution.

Weirdly enough, in my current testing, typing `-center_res 1024x768` or `-center_res 1280x1024` has no effect when playing with a 32:9 resolution. I have no idea why.

The culprit here seems to be the logic as explained with the [-center_res](https://wiki.hard-light.net/index.php/Command-Line_Reference#-center_res)` command line option:

> By default, if the screen resolution's aspect ratio is wider than 7:2, most 2D elements utilize only the center 3/10 of the screen area

Now, this creates some problems for BP. As whilst for a lot of the custom hud hackery we've taken into account a whole lot of situations, my predecessors did not account for the edge-case of someone running a setup of three 5:4 monitors. Oops. If they had done so, they would obviously have accounted for FSO then trying to squeeze the HUD into an aspect ratio of 9:8, or 6:5, or - in the case of users of a 32:9 monitor - 16 : 15.

_however_

In the name of being forward looking, I would like for FSO's default behaviour to be changed here. It's relatively safe to assume that people trying to run FSO at a aspect ratio wider than 7:2 (31.5:9) are in fact using a singular 32:9 monitor, and would not like the hud to be squeezed into an nearly 1:1 rectangle in the middle of the screen.

Having now listed out all that pre-amble, I'd like for three things to happen:

1. Investigate why the -center_res command doesn't function when specifying a 4:3 -center_res on a 32:9 -res, but does work when specifying a 16:9 -center_res on a 32:9 -res.
2. Change the hud scaling default so it never tries to scale the hud to an aspect ratio that's smaller then 4:3 (which is, after all, the FS2 default)
3. expose the -center_res option inside the ingame options menu so that in case other weird edge cases prop up, people can simply select the hud-resolution they want from within the game itself.