Add a setting to limit the number of quicksaves the game keeps

[mikeman7918]

I tend to quicksave a lot.  In my current game, I've done it exactly 994 times.  I know because the game has kept all of them.  Loading the list of quicksaves for my world now hangs the game for multiple seconds, and my game's file is multiple gigabytes.  As I continue using the save, these problems will just get worse.  At least until now, when I decided to just clear out my quicksaves manually.  But the game really shouldn't make you do that.

There is certainly an argument to be made that it's both useful and fun to be able to time travel around to any point in your save's past, but I think KSP1 had a better way of doing this in the form of named saves.   And though keeping multiple quicksaves is nice, I don't think I need a thousand of them.

My proposed solution is to add a setting for how many quicksaves the game will keep, and when the limit is reached the oldest quicksave is deleted to make room.  Similar to how the game already handles autosaves.  The default number of retained quicksaves could be a large but reasonable number like 100, with the setting to keep all of them or to change the number.  Named saves could be retained indefinitely.

Edited January 28 by mikeman7918