Add typed mock factory utilities for testing #5583

Job	Run time
build-and-check	2m 57s
test-integration-packages/internal	1m 10s
test-integration-packages/billing	1m 9s
test-integration-sdk	41s
test-integration-web	53s
test-integration-packages/agent-runtime	42s
test-integration-cli	42s
test-common	41s
test-cli	1m 17s
test-integration-common	39s
test-sdk	45s
test-packages/internal	49s
test-.agents	36s
test-packages/billing	42s
test-web	47s
test-packages/agent-runtime	56s
	15m 26s

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