pqProxyInformationWidget: avoid creating multiple delegates.
requested to merge utkarsh.ayachit/paraview:19517-memory-leak-in-pqproxyinformationwidget into master
pqProxyInformationWidget now creates all item delegates in the constructor once. This avoids the bug reported in #19517 (closed) which can cause slowdown for long running animations.
Closes #19517 (closed)