Add result count to search and rewrite scroll past end feature (#946)

* Restore colours to dark theme search-replace icon
* Implement a working search result counter
* Disable scroll past end feature and clean up search/replace and update test
* Re-implement scroll past end feature as a static distance
* Stop the search box from resizing on every search

tests/reference/baseConfig_novelwriter.conf

@@ -42,7 +42,7 @@ repsquotes = True
 repdquotes = True
 repdash = True
 repdots = True
-scrollpastend = True
+scrollpastend = 25
 autoscroll = False
 autoscrollpos = 30
 fmtsinglequote = ‘, ’