Instrument SpanContextFromContext to return the span context of the auto generated span #4111

Job	Run time
kubernetes-test (v1.26.0, nethttp)	4m 9s
kubernetes-test (v1.26.0, nethttp_custom)	3m 52s
kubernetes-test (v1.26.0, gin)	4m 15s
kubernetes-test (v1.26.0, databasesql)	4m 23s
kubernetes-test (v1.26.0, grpc)	4m 56s
kubernetes-test (v1.26.0, otelglobal)	3m 38s
kubernetes-test (v1.26.0, kafka-go)	3m 27s
	28m 40s

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