Show activating status in the status bar

[Radeonmann]

It should be indicated in the status bar, that the extension is currently in activation phase (e.g. during parsing of file tree, searching of installed AS versions, ...).
This could be done similar to the JS/TS extension:

By clicking on the status bar information, a notification could be opened which shows some kind of additional information or the current activity.

Tasks:

• Show status bar information during whole activation phase
• Show additional information / current activity in notification on click of status bar
• Still show errors / warnings as notifications