Datastore: revamp bench suite

[teh-cmc]

This reworks the datastore benchmark suite to actually cover all of the important stuff, and make it scalable to more parameters in the future (without breaking existing graphs).
This is a prerequisite for #1619 and in particular #1727 and its upcoming follow ups.

Needs to be merged in separately as it breaks existing benchmarks.

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Benchmark suite	Current: 29626cd
datastore/num_rows=1000/num_instances=1000/packed=false/insert/default	12625677 ns/iter (± 607274)
datastore/num_rows=1000/num_instances=1000/packed=false/insert/bucketsz=0	14646870 ns/iter (± 1133610)
datastore/num_rows=1000/num_instances=1000/packed=false/insert/bucketsz=2	13995839 ns/iter (± 782248)
datastore/num_rows=1000/num_instances=1000/packed=false/insert/bucketsz=32	13002161 ns/iter (± 984171)
datastore/num_rows=1000/num_instances=1000/packed=false/insert/bucketsz=2048	12813783 ns/iter (± 906175)
datastore/num_rows=1000/num_instances=1000/packed=true/insert/default	12206704 ns/iter (± 599724)
datastore/num_rows=1000/num_instances=1000/packed=true/insert/bucketsz=0	14043694 ns/iter (± 609431)
datastore/num_rows=1000/num_instances=1000/packed=true/insert/bucketsz=2	13270571 ns/iter (± 772281)
datastore/num_rows=1000/num_instances=1000/packed=true/insert/bucketsz=32	11689675 ns/iter (± 452193)
datastore/num_rows=1000/num_instances=1000/packed=true/insert/bucketsz=2048	11165205 ns/iter (± 474775)
datastore/num_rows=1000/num_instances=1000/packed=false/latest_at/default	1856 ns/iter (± 20)
datastore/num_rows=1000/num_instances=1000/packed=false/latest_at/bucketsz=0	1873 ns/iter (± 0)
datastore/num_rows=1000/num_instances=1000/packed=false/latest_at/bucketsz=2	1865 ns/iter (± 1)
datastore/num_rows=1000/num_instances=1000/packed=false/latest_at/bucketsz=32	1867 ns/iter (± 2)
datastore/num_rows=1000/num_instances=1000/packed=false/latest_at/bucketsz=2048	1854 ns/iter (± 33)
datastore/num_rows=1000/num_instances=1000/packed=true/latest_at/default	1869 ns/iter (± 18)
datastore/num_rows=1000/num_instances=1000/packed=true/latest_at/bucketsz=0	1877 ns/iter (± 2)
datastore/num_rows=1000/num_instances=1000/packed=true/latest_at/bucketsz=2	1872 ns/iter (± 6)
datastore/num_rows=1000/num_instances=1000/packed=true/latest_at/bucketsz=32	1885 ns/iter (± 3)
datastore/num_rows=1000/num_instances=1000/packed=true/latest_at/bucketsz=2048	1883 ns/iter (± 0)
datastore/num_rows=1000/num_instances=1000/packed=false/latest_at_missing/primary/default	286 ns/iter (± 1)
datastore/num_rows=1000/num_instances=1000/packed=false/latest_at_missing/secondaries/default	438 ns/iter (± 0)
datastore/num_rows=1000/num_instances=1000/packed=false/latest_at_missing/primary/bucketsz=0	281 ns/iter (± 0)
datastore/num_rows=1000/num_instances=1000/packed=false/latest_at_missing/secondaries/bucketsz=0	444 ns/iter (± 6)
datastore/num_rows=1000/num_instances=1000/packed=false/latest_at_missing/primary/bucketsz=2	280 ns/iter (± 0)
datastore/num_rows=1000/num_instances=1000/packed=false/latest_at_missing/secondaries/bucketsz=2	443 ns/iter (± 1)
datastore/num_rows=1000/num_instances=1000/packed=false/latest_at_missing/primary/bucketsz=32	282 ns/iter (± 1)
datastore/num_rows=1000/num_instances=1000/packed=false/latest_at_missing/secondaries/bucketsz=32	443 ns/iter (± 0)
datastore/num_rows=1000/num_instances=1000/packed=false/latest_at_missing/primary/bucketsz=2048	282 ns/iter (± 0)
datastore/num_rows=1000/num_instances=1000/packed=false/latest_at_missing/secondaries/bucketsz=2048	439 ns/iter (± 0)
datastore/num_rows=1000/num_instances=1000/packed=true/latest_at_missing/primary/default	281 ns/iter (± 0)
datastore/num_rows=1000/num_instances=1000/packed=true/latest_at_missing/secondaries/default	437 ns/iter (± 1)
datastore/num_rows=1000/num_instances=1000/packed=true/latest_at_missing/primary/bucketsz=0	280 ns/iter (± 0)
datastore/num_rows=1000/num_instances=1000/packed=true/latest_at_missing/secondaries/bucketsz=0	444 ns/iter (± 0)
datastore/num_rows=1000/num_instances=1000/packed=true/latest_at_missing/primary/bucketsz=2	281 ns/iter (± 0)
datastore/num_rows=1000/num_instances=1000/packed=true/latest_at_missing/secondaries/bucketsz=2	447 ns/iter (± 0)
datastore/num_rows=1000/num_instances=1000/packed=true/latest_at_missing/primary/bucketsz=32	281 ns/iter (± 0)
datastore/num_rows=1000/num_instances=1000/packed=true/latest_at_missing/secondaries/bucketsz=32	444 ns/iter (± 0)
datastore/num_rows=1000/num_instances=1000/packed=true/latest_at_missing/primary/bucketsz=2048	282 ns/iter (± 0)
datastore/num_rows=1000/num_instances=1000/packed=true/latest_at_missing/secondaries/bucketsz=2048	438 ns/iter (± 0)
datastore/num_rows=1000/num_instances=1000/packed=false/range/default	12517856 ns/iter (± 924973)
datastore/num_rows=1000/num_instances=1000/packed=false/range/bucketsz=0	2216396 ns/iter (± 9037)
datastore/num_rows=1000/num_instances=1000/packed=false/range/bucketsz=2	2188885 ns/iter (± 10207)
datastore/num_rows=1000/num_instances=1000/packed=false/range/bucketsz=32	1957717 ns/iter (± 8345)
datastore/num_rows=1000/num_instances=1000/packed=false/range/bucketsz=2048	1864529 ns/iter (± 6538)
datastore/num_rows=1000/num_instances=1000/packed=true/range/default	12318758 ns/iter (± 392622)
datastore/num_rows=1000/num_instances=1000/packed=true/range/bucketsz=0	2212547 ns/iter (± 6209)
datastore/num_rows=1000/num_instances=1000/packed=true/range/bucketsz=2	2178050 ns/iter (± 7677)
datastore/num_rows=1000/num_instances=1000/packed=true/range/bucketsz=32	1920285 ns/iter (± 12660)
datastore/num_rows=1000/num_instances=1000/packed=true/range/bucketsz=2048	1857672 ns/iter (± 4359)