Option to start the browser without disk cache

[bsclifton]

Carried over from brave/browser-laptop#629

It would be great to have an option to have no disk cache, Chromium creates tons of cache every session, is also not good for SSD disks.

So, i would either have a way to limit disk cache in memory size or the option to switch it off completely.

As suggested in the issue, this could be addressed by adding a new preference to settings