Disable Add/Remove component buttons for linked object

[keianhzo]

Description
Library linked data-blocks are immutable unless overridden. We currently allow users to add/remove components in library linked data-blocks which leads to errors.

To Reproduce
Steps to reproduce the behavior:

• Add a linked object
• Click on the add component button

Expected behavior
The add/remove button shouldn't be enabled. Additionally we should show the reason in the builtin tooltip if possible or find a way of show the reason in the UI.

Like in this builtin operator: