UI: Custom Windows Cursors for VSE Handles

VSE has three mouse cursors defined, WM_CURSOR_LEFT_HANDLE,
WM_CURSOR_RIGHT_HANDLE, and WM_CURSOR_BOTH_HANDLES that are currently
always using our default cursor format. This format works on all
platforms but does not support multiple sizes or antialiasing. This
PR makes these use custom cursors (created by Pablo Vazquez) on the
Windows platform.

Pull Request: https://projects.blender.org/blender/blender/pulls/125252

release/windows/icons/winblender.rc

@@ -36,6 +36,9 @@ splitv_cursor CURSOR "cursors/splitv.cur"
 zoomin_cursor CURSOR "cursors/zoomin.cur"
 zoomout_cursor CURSOR "cursors/zoomout.cur"
 forbidden_cursor CURSOR "cursors/forbidden.cur"
+handle_left_cursor CURSOR "cursors/handle_left.cur"
+handle_right_cursor CURSOR "cursors/handle_right.cur"
+handle_both_cursor CURSOR "cursors/handle_both.cur"
 
 IDR_VERSION1 VERSIONINFO
 FILEVERSION BLEN_VER_RC_1, BLEN_VER_RC_2, BLEN_VER_RC_3, BLEN_VER_RC_4