Don't cache display rectangle and client rectangle as they can both change
during the program lifetime (especially the latter which changes whenever
taskbar is moved or shown/hidden) and retrieving them every time they're
needed doesn't seem to be a problem performance-wise anyhow.
We still cache the list of all the monitors, ideally we'd refresh it when we
receive a notification about a display being [dis]connected.
Closes#4582.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65555 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
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