Generate test config file from function instead of file #1376

Job	Run time
check	37s
clippy	44s
test	2m 22s
audit	21s
rustfmt	6s
cross-mips64	35s
cross-mips64el	38s
cross-armv7	48s
cross-mips	48s
integration-test-five-nodes	18m 31s
cross-mipsel	52s
legacy_integration-test-with-backcompat	22m 53s
legacy_integration-test	26m 59s
cross-aarch64	49s
integration-test-eth-payments	25m 10s
integration-test-debts	21m 18s
integration-test-althea-payment	28m 28s
	2h 31m 59s

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