Change the default mode of the erasor tool

[SpeeQz1]

Description
Changing the eraser instead of deleting the canvas itself and leaving transparent pixels, to instead use white color by default.
It should still have the option to remove the canvas with transparent pixels but it should be a mode option which the user has to manually toggle.

Additional context
Some people have complained that it's annoying the eraser tool by default removes the canvas instead of just placing white on top of it.

[cameronwhite]

I'm not sure this should be the default behaviour, but more opinions on this would be good!
For example, Paint.NET's eraser tool also erases to transparent, not white

By the way, this can sort of be done already by right clicking in the eraser tool, which erases to the secondary color (often white, at least by default)