Make flow/task engine release slots after a timeout #15834

Job	Run time
docker, python:3.9	5m 7s
Server Tests - python:3.9, postgres:14	3m 29s
docker, python:3.10	5m 4s
Server Tests - python:3.10, postgres:14	3m 21s
docker, python:3.11	5m 0s
Server Tests - python:3.11, postgres:14	3m 25s
docker, python:3.12	5m 11s
Server Tests - python:3.12, postgres:14	3m 33s
Server Tests - python:3.9, sqlite	4m 53s
Server Tests - python:3.10, sqlite	5m 32s
Server Tests - python:3.11, sqlite	4m 38s
Server Tests - python:3.12, sqlite	5m 27s
Client Tests - python:3.9, postgres:14	6m 55s
Client Tests - python:3.10, postgres:14	7m 3s
Client Tests - python:3.11, postgres:14	6m 12s
Client Tests - python:3.12, postgres:14	6m 51s
	1h 21m 41s

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