feat(bw6-761): Miller loop using direct sextic extension (#608) #122

Job	Run time
staticcheck	1m 12s
test (1.23.x, ubuntu-latest-128)	3m 58s
test (1.23.x, windows-latest)	5m 59s
test (1.23.x, macos-latest)	3m 16s
slack-notifications / notify_slack	1s
	14m 26s

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