commonlib: Add indicator for new output to TabbedOutputPanel

[ricekot]

A green dot is added to the top right corner of tab icons in the tabbed output panel when new output is appended to those tabs.

The changelog was not updated because the tabbed output panel hasn't been released yet and there's already a note about it.

Partially addresses #6044 (comment).

[psiinon]

Checkmarx One – Scan Summary & Details – 8212353e-9d8d-4eaa-808d-b8a386d28fc2

Fixed Issues (3)

Great job! The following issues were fixed in this Pull Request

Severity	Issue	Source File / Package
	Heap_Inspection	/addOns/authhelper/src/test/java/org/zaproxy/addon/authhelper/AuthUtilsUnitTest.java: 864
	Heap_Inspection	/addOns/authhelper/src/test/java/org/zaproxy/addon/authhelper/AuthUtilsUnitTest.java: 840
	Heap_Inspection	/addOns/authhelper/src/test/java/org/zaproxy/addon/authhelper/AuthUtilsUnitTest.java: 817

[thc202]

When there's a single output tab the indicator does not disappear.

[ricekot]

Thank you, added a mouse listener to the text output so the indicator disappears when the mouse enters the output panel.
Another change I made was to have the indicator show even if the tab is the current selected tab. I think that's a more consistent behaviour and results in a better UX.

Some implementation notes:

• The overlay icon construction was moved out of the lambda so we're no longer incurring that overhead on each change event
• Instead of adding a reference to the output panel in the change listener, the TabbedOutputPanel now maintains a map from the output source to corresponding listener. This is used to remove the listener when the output source is unregistered or clear() is called.

[kingthorin]

Still LGTM

[thc202]

Thank you!