Grow text editor control to contain all text in generic wxDataViewCtrl.

Implement the behavior that Explorer uses: if the column is too narrow
to fit the current text of a cell into it, don't create a too-small text
control for it, because it is annoying and confusing (typically, the
beginning of the text would be hidden, which is disastrous if it happens
to contain numbers). Instead, grow the text control to be larger than
the column for more comfortable editing.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75183 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Cancel editing in generic wxDVC when clicking outside of the editor control.

wxDataViewCtrl should behave as Explorer does on Windows: when an inline
editor control is open, clicking outside of it should close the editor
(preserving changes) in most cases - as a rule of thumb, when the
subsequent action could interfere with the editor somehow.

This was implemented by watching for focus change and so ignored clicks
made on non-focusable controls outside of wxDVC's main window area.  In
particular, clicks on the list's header were ignored, even though they
could result in modifications of the editor's position or size.

Don't finish editing when the user right-clicks on the header,
consistently with Explorer.  Opening the menu likewise still doesn't
finish editing, it is needed for access to editing operations.

Fixes #15152.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75184 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775