libtaskmanager: improve efficiency when window icon frequently changes
Reason for the change
Don't wipe the whole appData cache entry when only the icon changes because constructing the cache requires querying all applications on the local disk.
Add NET::WMIcon to cachable properties as it's usually expensive to update icons.
Test plan
Pass xwindowtaskmanagertest
Modify the interval in libtaskmanager/autotests/data/windows/bug478831.py
to 1 and run the script
Screenshots or screen recordings
Bugs fixed
BUG: 487390 FIXED-IN: 6.1.2
Edited by Fushan Wen