docs: revise last chapters of customizations #34467

Job	Run time
setup	1m 56s
Shard (0) Unit Tests	9m 2s
integration-tests-packages	13m 12s
Shard (0) HTTP Integration Tests	12m 5s
Shard (1) Unit Tests	5m 22s
Shard (0) Module Integration Tests	10m 49s
Shard (1) HTTP Integration Tests	8m 56s
Shard (1) Module Integration Tests	9m 31s
unit-tests	1s
integration-tests-modules	1s
integration-tests-http	1s
	1h 10m 56s

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