Bitmap::load_from_file("foo.png", 2) will now look for "foo-2x.png" and
try load that as a bitmap with scale factor 2 if it exists. If it
doesn't, it falls back to the 1x bitmap as normal.
Only places that know that they'll draw the bitmap to a 2x painter
should pass "2" for the second argument.
Use this new API in WindowServer for loading window buttons and
cursors.
As a testing aid, ctrl-shift-super-i can force HighDPI icons off in
HighDPI mode. Toggling between low-res and high-res icons makes it easy
to see if the high-res version of an icon looks right: It should look
like the low-res version, just less jaggy.
We'll likely have to grow a better API for loading scaled resources, but
for now this suffices.
Things to check:
- `chres 640 480` followed by `chres 640 480 2` followed by
`chres 640 480`
- window buttons in window context menu (in task bar and on title bar)
still have low-res icons
- ctrl-shift-super-i in high-res mode toggles sharpness of window
buttons and of arrow cursorf
- arrow cursor hotspot is still where you'd expect
