feat(core-flows,medusa): Add API to update cart's customer #33540

Job	Run time
setup	2m 25s
integration-tests-packages	13m 1s
Shard (0) Module Integration Tests	11m 2s
Shard (0) Unit Tests	8m 48s
Shard (1) Module Integration Tests	9m 42s
Shard (0) HTTP Integration Tests	12m 14s
Shard (1) Unit Tests	5m 10s
Shard (1) HTTP Integration Tests	8m 59s
unit-tests	1s
integration-tests-modules	1s
integration-tests-http	1s
	1h 11m 24s

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