Changes in default configuration for Krita 5

I changed four different configuration settings to have different values by default than they have before this MR.

1. Default PDF dpi to 300 on import.

   • I often use the PDF import option for A4 images. I always have to change from 100 to 300. While the real fix would be to remember the configuration for a user, it's reasonable to change the default dpi option to be 300 as well. For comparison, see that the default templates for A4 images are either 300 dpi or 600 dpi. And since PDF documents often contain text, having low dpi causes the text to be less clear. While Krita is not for PDF documents editing, having sane defaults doesn't really cost much. And there is no danger of users getting huge images accidentally since I don't think I've ever seen a PDF document bigger than A3.

2. Change autosave interval to 7 minutes.

   • I actually have it much more often myself; I used to have 5 minutes, now I have 3 minutes. 15 minutes is a bit long time and you can lose quite a lot of work; smaller interval would help there (after starting to use 3 minutes, I've never lost any work that I was heartbroken about, because it was only some very latest strokes). I believe the 15 minutes interval was selected when autosave was still in the foreground thread and disruptive to users. Since it can cause little performance drops though, I decided to go somewhat "safe" route and use some kind of compromise between my default value and the current value. (For comparison, David Revoy has its autosave set to 3 minutes as well (though he turned off autosave notifications).)

3. Set Crop Tool to have "Grow" checked by default.

   • There are no real downsides, since the tool still snaps to the image edges if anyone needs it, and if someone don't want this behaviour for some very specific for their workflow reasons, they can still check it in the right-click options. However, new users coming to Krita, especially from other software, expect the Crop Tool to be able to enlarge the canvas as well. Artists like Borodante on youtube use this to fix/change composition etc.

4. Instant Preview for Move Tool.

   • I always used Move Tool as the WYSIWYG and quick version of Transform Tool: you could see pixels exactly, use the arrow keys, and it would activate without clicking on the canvas. In Krita 5 however it uses Instant Preview by default, which doesn't update when the user zooms in or out. It means that it's no longer showing the pixels correctly if the user does it (quick test: zoom out a lot, select something, use Move Tool, zoom in a lot, you'll see everything is smoothed out compared to the outside of the selection). Since moving is not that performance heavy anyway, it makes sense to me to turn the Instant Preview off by default. Otherwise it looks like a "regression".

Test Plan

Formalities Checklist

• I confirmed this builds.
• I confirmed Krita ran and the relevant functions work.
• I tested the relevant unit tests and can confirm they are not broken. (If not possible, don't hesitate to ask for help!)
• I made sure my commits build individually and have good descriptions as per KDE guidelines.
• I made sure my code conforms to the standards set in the HACKING file.
• I can confirm the code is licensed and attributed appropriately, and that unattributed code is mine, as per KDE Licensing Policy.