sliceop/f64s: improve Take performances
sliceop/f64s: improve Take performances

name                old time/op    new time/op    delta
Take/Len=2-8          2.69ns ± 1%    2.71ns ± 2%   +0.75%  (p=0.043 n=18+18)
Take/Len=4-8          3.18ns ± 1%    3.23ns ± 3%   +1.27%  (p=0.005 n=19+20)
Take/Len=8-8          3.83ns ± 1%    3.73ns ± 1%   -2.69%  (p=0.000 n=20+19)
Take/Len=128-8        44.1ns ± 4%    35.9ns ± 2%  -18.61%  (p=0.000 n=20+20)
Take/Len=1024-8        337ns ± 2%     280ns ± 6%  -16.73%  (p=0.000 n=19+20)
Take/Len=1048576-8    1.37ms ± 3%    1.31ms ± 5%   -3.97%  (p=0.000 n=19+20)

name                old alloc/op   new alloc/op   delta
Take/Len=2-8           0.00B          0.00B          ~     (all equal)
Take/Len=4-8           0.00B          0.00B          ~     (all equal)
Take/Len=8-8           0.00B          0.00B          ~     (all equal)
Take/Len=128-8         0.00B          0.00B          ~     (all equal)
Take/Len=1024-8        0.00B          0.00B          ~     (all equal)
Take/Len=1048576-8     0.00B          0.00B          ~     (all equal)

name                old allocs/op  new allocs/op  delta
Take/Len=2-8            0.00           0.00          ~     (all equal)
Take/Len=4-8            0.00           0.00          ~     (all equal)
Take/Len=8-8            0.00           0.00          ~     (all equal)
Take/Len=128-8          0.00           0.00          ~     (all equal)
Take/Len=1024-8         0.00           0.00          ~     (all equal)
Take/Len=1048576-8      0.00           0.00          ~     (all equal)

go-hep/hep,go-hep/hep