Add clearButtonEnabled property to filter bar

[isf63]

Same as https://github.com/lxqt/lxqt-panel/pull/1898

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Unrelated, while compiling there's a GLib cast warning:

[ 40%] Building CXX object src/CMakeFiles/lxqt-archiver.dir/archiver.cpp.o
lxqt-archiver/src/archiver.cpp: In static member function ‘static void Archiver::freeStrsGList(GList*)’:
lxqt-archiver/src/archiver.cpp:355:26: warning: cast between incompatible function types from ‘void (*)(gpointer)’ {aka ‘void (*)(void*)’} to ‘GFunc’ {aka ‘void (*)(void*, void*)’} [-Wcast-function-type]
  355 |     g_list_foreach(strs, (GFunc)g_free, nullptr);
      |

[tsujan]

Unrelated, while compiling there's a GLib cast warning:

See https://github.com/lxqt/lxqt-archiver/pull/406 — recently I dealt with similar GLib nuisances elsewhere ;)