Closing a tooltip opened from keyboard does not raise ToolTipClosing event

[SamBent]

• .NET Core Version: 3.0 and above
• Windows version: all
• Does the bug reproduce also in WPF for .NET Framework 4.8?: Yes
• Is this bug related specifically to tooling in Visual Studio (e.g. XAML Designer, Code editing, etc...)? no

• Security issues and bugs should be reported privately, learn more via our responsible disclosure guidelines.

  Problem description:

1. Run (revised) sample app attached to #4612
2. Press TAB repeatedly until focus arrives on the TextBox labelled "TextBox"
3. Wait for tooltip to appear (and note the ToolTipOpening event is recorded in the ListBox)

4. Press TAB again

   Actual behavior: Tooltip disappears, but the ToolTipClosing event isn't raised.

   Expected behavior: ToolTipClosing event should be raised (and recorded in the ListBox).

By contrast, move the mouse into the TextBox, wait for the tooltip, then move the mouse upwards away from the TextBox. The ToolTipOpening and ToolTipClosing events are both raised (and recorded in the ListBox).

The ToolTipClosing event should be raised whenever a tooltip closes.

[SamBent]

Fixed by the tooltip work in 6.0-preview7.