Squashed commit of the following:

commit bbe5f26
Author: crusaderky <[email protected]>
Date:   Wed Jun 1 15:13:06 2022 +0100

    polish

commit d7473e7
Author: crusaderky <[email protected]>
Date:   Wed Jun 1 14:00:43 2022 +0100

    fixes

commit d36bb3f
Author: crusaderky <[email protected]>
Date:   Wed Jun 1 12:47:46 2022 +0100

    docstring

commit 54b3498
Author: crusaderky <[email protected]>
Date:   Wed Jun 1 12:46:32 2022 +0100

    tweaks

commit 71a31a7
Merge: a032754 715d7be
Author: crusaderky <[email protected]>
Date:   Wed Jun 1 12:36:52 2022 +0100

    Merge branch 'main' into WSMR/forgotten_data_needed

commit a032754
Author: crusaderky <[email protected]>
Date:   Wed Jun 1 11:40:22 2022 +0100

    data_needed only contains tasks in fetch state

commit 9280162
Author: crusaderky <[email protected]>
Date:   Tue May 31 16:00:52 2022 +0100

    Refactor: new module distributed.collections

commit 9ef92e7
Author: crusaderky <[email protected]>
Date:   Tue May 31 16:00:25 2022 +0100

    Rename test

commit 59e5457
Author: crusaderky <[email protected]>
Date:   Tue May 31 15:59:35 2022 +0100

    Test deadlock
Merge remote-tracking branch 'refs/remotes/upstream/main'

Conflicts:
	distributed/tests/test_collections.py
	distributed/tests/test_dask_collections.py