Allow using wxCollapsibleHeaderCtrl in wxGTK too

The implementation file for this control somehow wasn't used in wxGTK build,
fix this and, in fact, include it in common sources as there is only a generic
implementation of this control so far.

Closes #17309.

build/files

@@ -620,6 +620,7 @@ GUI_CMN_SRC =
     src/generic/buttonbar.cpp
     src/generic/choicdgg.cpp
     src/generic/choicbkg.cpp
+    src/generic/collheaderctrlg.cpp
     src/generic/combog.cpp
     src/generic/dcpsg.cpp
     src/generic/dirctrlg.cpp
@@ -1186,7 +1187,6 @@ GTK1_SRC =
     # Generic implementations used by wxGTK1:
     src/generic/accel.cpp
     src/generic/clrpickerg.cpp
-    src/generic/collheaderctrlg.cpp
     src/generic/collpaneg.cpp
     src/generic/colrdlgg.cpp
     src/generic/dirdlgg.cpp
@@ -1351,7 +1351,6 @@ MOTIF_SRC =
     src/motif/xmcombo/xmcombo.c
     # Generic files used by wxMotif:
     src/generic/clrpickerg.cpp
-    src/generic/collheaderctrlg.cpp
     src/generic/collpaneg.cpp
     src/generic/colrdlgg.cpp
     src/generic/dirdlgg.cpp
@@ -1579,7 +1578,6 @@ MSW_DESKTOP_LOWLEVEL_HDR =
 
 MSW_SRC =
     src/generic/clrpickerg.cpp
-    src/generic/collheaderctrlg.cpp
     src/generic/collpaneg.cpp
     src/generic/filepickerg.cpp
     src/generic/fontpickerg.cpp
@@ -1641,7 +1639,6 @@ MSW_SRC =
     src/msw/treectrl.cpp
 MSW_HDR =
     wx/generic/clrpickerg.h
-    wx/generic/collheaderctrl.h
     wx/generic/collpaneg.h
     wx/generic/filepickerg.h
     wx/generic/fontpickerg.h
@@ -1938,7 +1935,6 @@ OSX_COMMON_SRC =
     # Generic implementations used by wxOSX:
     src/generic/caret.cpp
     src/generic/clrpickerg.cpp
-    src/generic/collheaderctrlg.cpp
     src/generic/collpaneg.cpp
     src/generic/colrdlgg.cpp
     src/generic/dirdlgg.cpp
@@ -2212,7 +2208,6 @@ COCOA_SRC =
     src/generic/accel.cpp
     src/generic/caret.cpp
     src/generic/clrpickerg.cpp
-    src/generic/collheaderctrlg.cpp
     src/generic/collpaneg.cpp
     src/generic/colrdlgg.cpp
     src/generic/fdrepdlg.cpp
@@ -2327,7 +2322,6 @@ UNIV_SRC =
     $(UNIV_PLATFORM_SRC)
     src/generic/accel.cpp
     src/generic/clrpickerg.cpp
-    src/generic/collheaderctrlg.cpp
     src/generic/collpaneg.cpp
     src/generic/colrdlgg.cpp
     src/generic/dirdlgg.cpp