Introduce `ahUSDT` (#1236) #760

Job	Run time
Task check format	39s
Task check features (runtime/darwinia)	1m 44s
Task check features (runtime/crab)	5m 33s
Task check features (runtime/pangoro)	1m 26s
Task check features (runtime/pangolin)	1m 35s
Task build darwinia	50m 27s
Task test darwinia	50m 9s
Task check runtimes	0s
Task check EVM	0s
Task checks cleaning	2s
	1h 51m 35s

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