Extend shared worker

[bastianjoel]

resolves #3248
resolves #3259
resolves #3401

This PR involves a lot of cleanup in the shared worker. Also tests were added.

TODO:

• Autoupdate
  • Add tests to autoupdate part
  • Rework unexpected stream resolve handling (session termination, restart)
  • Fix issues with stream pausing
  • Longpolling
• ICC
  • Implement icc protocol in shared worker
  • Update icc adapter
• Auth via shared worker

[luisa-beerboom]

Using accessibility modifiers for constructors is not consistently done in the client. I don't like introducing this rule right now with this PR.

It is not an introduction, it is overwhelmingly done in the client for the simple reason that it is an established convention to put visibility modifiers on everything. The exceptions where it is inconsistent are merely instances that were not caught during the code review.

I am not asking you to fix it everywhere right now, I am asking you to fix it in your code

[luisa-beerboom]

Or fix this in another PR

[bastianjoel]

@emanuelschuetze @MSoeb @Elblinator @rrenkert Maybe it is not completely obvious by the title and description but this PR includes the longpolling implementation and is finished since last week.
If anybody is feeling qualified to test this feel free to add a review.

The performance tool has a new tool broken-proxy to test this.

[rrenkert]

Works as expected.

But the warning sign is not centered:

[bastianjoel]

>:(

[bastianjoel]

This is a problem with the banner service. Offline mode and out of sync have the same problem. For that reason I think this is totally unrelated to this PR. Please open another issue.

[Elblinator]

I created a new Issue
see #3506

change requests were moved to another Issue