Update behavior of read-files to truncate after 100k chars #6053

Job	Run time
build-and-check	3m 14s
test-integration-packages/internal	1m 9s
test-integration-packages/billing	1m 13s
test-integration-web	46s
test-integration-sdk	1m 25s
test-integration-packages/agent-runtime	38s
test-integration-common	45s
test-integration-cli	41s
test-packages/agent-runtime	46s
test-common	43s
test-packages/billing	43s
test-sdk	48s
test-packages/internal	51s
test-cli	59s
test-web	48s
test-.agents	39s
	16m 8s

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