[20_13] Do not add duplicated values to copy_always to avoid stack overflow

[wind1900]

What

Add check before adding new values to edit_interface_rep::copy_always in function edit_interface_rep::apply_changes().
New rectangle will be added to copy_always if copy_always is empty/nil or the first item of copy_always is not equal to newly added value.

Why

Since apply_changes() will be called when the window receives any event, copy_always will become very large and cause stack overflow when it's cleared.
The copy_always is a linked list and when it's cleared, the destructor is called from head to tail recursively, causing stack overflow.

How to test your changes?

That's the potential risk: I can only test it on Windows with few scenarios, I don't know the result in Linux, Mac.

already run xmake run --yes -vD --group=tests and xmake run --yes -vD --group=integration_tests

The investigations below are all in Windows environment.

Where is the code to clear copy_always?

In edit_interface_rep::scroll_to() and edit_interface_rep::set_extents(), by using copy_always = rectangles ().

When will copy_always be cleared?

scroll_to() is called when the cursor is moved out of current view.
I can't add breakpoint in set_extents(), I don't know when will it will be called.

What's the purpose of copy_always?

The comment says it's used for wiping out cursor.
However I think it doesn't do anything now.
I comment out the code that uses it, get nothing wrong.
But removing it is more dangerous.

Where is copy_always used?

In edit_interface_rep::draw_pre() and edit_interface_rep::draw_with_shadow().

In draw_pre(), it will go through all rectangles in copy_always and call win->put_shadow(), but it doesn't draw anything at all.
Because in qt_renderer_rep::put_shadow(), painter == static_cast<qt_renderer_rep*> (ren)->painter is true and returns directly.

In draw_with_shadow(), it's only used if gui_interrupted() returns true, but gui_interrupted() doesn't return true in my machine.

These shadow functions are related to the double buffering, the behavior may be different in other OS.

In summary, I don't think it's necessary to store all the old rectangles in copy_always.
The latest ones ocr(old cursor) and ncr(new cursor) should be enough for cursor drawing stuff.

[da-liii]

CI已经修复，合并branch-1.2，再push一下，这个pr就可以正常通过CI了

[da-liii]

LGTM