The status message when a search does not yield any results is currently
shown for some milliseconds when using search-as-you-type within the
find/replace overlay. The reason for this are selection updates in the
editor performed before starting an incremental search, which are then
processed by JDT removing the status message immediately after it has
been defined. These selection updates are unnecessary, probably since
resetting the incremental base position has been streamlined.

This change removes obsolete logic for setting selections and comparing
current search results in the editor when performing incremental search.
It simplifies the implementation and ensures that status messages are
properly shown when the search does not yield any result.

Fixes https://github.com/eclipse-platform/eclipse.platform.ui/issues/1993