Add higher-res and consistent ProB logo for feature branding

de.prob.eventb.disprover.ui/about.ini

 aboutText=ProB Disprover (c) 2009-2024 https://prob.hhu.de/w/
-featureImage=icons/feature.png
+featureImage=icons/prob32.png

de.prob.symbolic/about.ini

 aboutText=ProB Symbolic Evaluation Support (c) 2013-2024 https://prob.hhu.de/w/
+featureImage=icons/prob32.png

de.prob.symbolic/build.properties

@@ -2,5 +2,6 @@ source.. = src/
 output.. = bin/
 bin.includes = META-INF/,\
                .,\
+               icons/,\
                about.ini,\
                plugin.xml

de.prob.ui/about.ini

 aboutText=ProB Animator (c) 2005-2024 https://prob.hhu.de/w/
-featureImage=icons/prob.png
+featureImage=icons/prob32.png