Add a16w8 per-op test for gelu #5610

Job	Run time
test-qnn / test-backend-linux (qnn, models) / linux-job	26m 58s
test-qnn / test-backend-linux (qnn, operators) / linux-job	15m 1s
test-qnn / test-backend-macos	-1s
test-qnn / package-golden-artifacts	2m 26s
	44m 24s

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