Also, this change fixes redundant checks the case when a monitor
does not exist. Now Ebitengine checks a monitor existence at the
initialization.
Closes#2145Closes#2795
Now the unit of Bounds is device-dependent pixels, and this is useless
and Ebitengine API always treat device-independent pixels. Rather,
this might confuse users.
Until we find a good solution, let's remove Bounds() for v2.6.
MonitorType itself is still useful to specify a monitor to show a
window.
Monitors can have different device scale factors, and in this case,
it doesn't make sense to use device-independent pixels as unit for
monitor positions and sizes.
Updates #2778
