Pgq

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* build: convert to pyproject.toml
* typing: add full typing
* ci: drop unmaintained actions

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Fixes:

* worker: another refactor for wait-behind - use dedicated code path for it,
following main path makes things too complicated. Fixes the problem of
missing node location events.
* nodeinfo: set more fields on dead node

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Fixes:

* status: fix crash on dead node

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Fixes:

* worker: fix merge-leaf watermark

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Fixes:

* worker: another wait-behind fix - avoid too eager switch.

Cleanups:

* Additional typing improvements.

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Fixes:

* worker: detect if wait-behind is finished