Add Halley's method via descent API #5

Job	Run time
downgrade (1.10, core)	16m 47s
test (core, 1.10, ubuntu-latest)	16m 39s
downgrade (1.10, downstream)	9m 8s
test (core, 1.10, macos-latest)	14m 12s
downgrade (1.10, wrappers)	11m 2s
test (core, 1.10, windows-latest)	27m 25s
test (core, 1, ubuntu-latest)	28m 50s
test (core, 1, macos-latest)	22m 24s
test (core, 1, windows-latest)	41m 41s
test (downstream, 1.10, ubuntu-latest)	8m 31s
test (downstream, 1.10, macos-latest)	5m 43s
test (downstream, 1.10, windows-latest)	12m 6s
test (downstream, 1, ubuntu-latest)	18m 24s
test (downstream, 1, macos-latest)	12m 56s
test (downstream, 1, windows-latest)	22m 51s
test (wrappers, 1.10, ubuntu-latest)	10m 1s
test (wrappers, 1.10, macos-latest)	7m 34s
test (wrappers, 1.10, windows-latest)	12m 56s
test (wrappers, 1, ubuntu-latest)	20m 36s
test (wrappers, 1, macos-latest)	13m 44s
test (wrappers, 1, windows-latest)	24m 11s
	5h 57m 41s

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