fix: set tty mode if force_tty is true in config file

[vandabbin]

Fixes: #1514

The force_tty menu option wasn't being applied when btop launched
even though it was being saved in the config file.

This fixes this by applying tty mode if this option is set to true in the config file

[deckstose]

This doesn't account for --no-tty+ config file force_tty = true

[vandabbin]

This doesn't account for --no-tty+ config file force_tty = true

Oh great catch!! I forgot that there was a no-tty cli option as well!

Although this does make it trickier. The no-tty command line option would leave force_tty as true in the config file so the menu option would continue to be backwards if btop is launched with --no-tty. I will have to think about this one some more to come up with something good

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I have compensated for this by changing the force_tty menu option to only toggle tty mode on if it is true and only toggle it off if it is false. I also added some platform specific code that basically disables the effect of toggling the force_tty menu option if a TTY was auto-detected (the same way it seems to be done when btop starts). I'm not 100% on the formatting I used for the compiler #if. I may have it indented poorly

• This way the user can launch with --no-tty and if force_tty is true in the config then the cli option over rules it (which I think makes sense).
• The menu option continues to show force_tty as true which is technically accurate (as a reflection of the config file) even if not currently in tty mode because it was done by a temporary measure (i.e. cli flag).
• If the menu option is then toggled off tty mode is not enabled as it would have been previously when all that did was flip the option.
• If the menu option force_tty is then toggled to true again it will reset to tty mode (overriding the cli option).
• If a TTY has been auto-detected toggling force_tty on or off will not have any visible effect.

I could possibly figure out some changes to make the force_tty menu option reflect the cli flag as well without saving it to the config file (if set by flag) when it exits, but I am not sure it is worth the extra work