add primitives for Thomas' spake2 #1038

Job	Run time
Tests (4.14.2, macos-latest)	7m 2s
Tests with OCaml 5 (5.2.1, ubuntu-latest)	5m 23s
Tests (4.14.2, ubuntu-latest)	5m 38s
Tests with OCaml 5 (5.2.1, macos-latest)	5m 40s
	23m 43s

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