Add a third "Tab Indicator" differentiating between "Current-Focused Tab" and "Current-Unfocused Tab"

STR:
Enable Draw a colored bar on active tab.
Give keyboard focus to a "not-editor" element (e.g. the Incremental Search Bar).

Result:
The Active tab focused indicator is used even when the tab does not have keyboard focus.

Suggested:
Three tab indicators.
1. "Current-Focused Tab".
2. "Current-Unfocused Tab".
3. "Current Tab in Other View".

-- The user would be able to instantly know if the editing window actually has keyboard focus.
-- The system color for "Active Window Title" could be set to "Current-Focused Tab".

Related: https://github.com/notepad-plus-plus/notepad-plus-plus/issues/8446.

Notepad++ v7.8.9 (32-bit)
Build time : Sep 5 2020 - 02:32:39
Path : C:---\notepad++.exe
Admin mode : ON
Local Conf mode : ON
OS Name : Windows 7 Enterprise (32-bit)
OS Build : 7601.23964
Current ANSI codepage : 1255
Plugins : ComparePlus.dll HTMLTag_unicode.dll MenuIcons.dll PythonScript.dll _CustomizeToolbar.dll

No files, tests, or implementation entry points are identified in the issue. Start by reproducing the STR with the active-tab indicator enabled and keyboard focus in the Incremental Search Bar; done means the UI distinguishes current-focused, current-unfocused, and current tabs in other views.