Fix the issue of the changes of the environment values not being set sometimes through fancy dialog box:
Make sure the environment value buffer is always reallocated before taking the values.
- Correctly handle the return values for WM_SIZING and WM_SIZE messages.
- Use NULL for hWndInsertAfter parameter of DeferWindowPos() when
we don't care about the Z-order.
- Specify SWP_NOMOVE for controls that don't move during resizing.
- Fix the IDOK and IDCANCEL buttons when resizing the environment
variables list dialog.
- Fix the dialog "moving" effect that happened whenever an attempt
was made to resize the dialog from either of the
top/left borders, or the top-right/top-left/bottom-left corners,
to a size smaller than the minimal one.
- Use DWLP_USER instead of GWLP_USERDATA when storing user-specific
data into the dialog, since the latter can be used internally by
the Win32 dialog manager implementation.
Improve the "Edit Environment Variable" dialog box to be functionally as similar to the one of Windows 10.
CORE-11733
- Improved the existing dialog box. In particular, allow it to be resizable.
- Implemented new "fancy" dialog box for variables containing multiple directories as values,
showing them in a list.
