sort: forward fixed-type slice sorting to slices package

Forwards the following functions to the slices package:

    sort.Ints
    sort.Strings
    sort.Float64s
    sort.IntsAreSorted
    sort.StringsAreSorted
    sort.Float64sAreSorted

benchstat results on the sort package's benchmarks:

goos: linux
goarch: amd64
pkg: sort
cpu: 11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz
SearchWrappers-8        58.10n ± 0%   58.43n ± 1%   +0.57% (p=0.004 n=10)
SortString1K-8          76.53µ ± 1%   66.04µ ± 2%  -13.71% (p=0.000 n=10)
SortString1K_Slice-8    71.99µ ± 1%   72.32µ ± 2%        ~ (p=0.481 n=10)
StableString1K-8        92.66µ ± 1%   92.10µ ± 2%   -0.61% (p=0.019 n=10)
SortInt1K-8             34.31µ ± 0%   11.49µ ± 2%  -66.50% (p=0.000 n=10)
SortInt1K_Sorted-8     2699.5n ± 1%   959.0n ± 3%  -64.47% (p=0.000 n=10)
SortInt1K_Reversed-8    3.990µ ± 1%   1.429µ ± 4%  -64.19% (p=0.000 n=10)
SortInt1K_Mod8-8       13.695µ ± 1%   5.129µ ± 2%  -62.55% (p=0.000 n=10)
StableInt1K-8           46.22µ ± 1%   46.80µ ± 1%        ~ (p=0.109 n=10)
StableInt1K_Slice-8     44.12µ ± 1%   44.32µ ± 2%        ~ (p=0.315 n=10)
SortInt64K-8            3.848m ± 0%   1.857m ± 2%  -51.76% (p=0.000 n=10)
SortInt64K_Slice-8      3.690m ± 0%   3.740m ± 0%   +1.36% (p=0.002 n=10)
StableInt64K-8          3.901m ± 0%   3.917m ± 0%   +0.42% (p=0.003 n=10)
Sort1e2-8               32.22µ ± 2%   32.40µ ± 2%        ~ (p=0.529 n=10)
Stable1e2-8             54.11µ ± 1%   54.11µ ± 1%        ~ (p=0.796 n=10)
Sort1e4-8               5.998m ± 1%   5.993m ± 1%        ~ (p=0.579 n=10)
Stable1e4-8             15.23m ± 0%   15.32m ± 0%   +0.59% (p=0.000 n=10)
Sort1e6-8               902.8m ± 0%   904.3m ± 0%        ~ (p=0.075 n=10)
Stable1e6-8              3.089 ± 0%    3.089 ± 0%        ~ (p=0.971 n=10)
geomean                 259.8µ        200.0µ       -22.99%

Most of the benchmarks are unaffected. The ones with significant reductions
are precisely for the functions that were forwarded.

This CL has to move some things around to avoid a circular dependency
between sort and slices. Since sort depends on slices now, nothing in
slices can depend on sort - not even in tests.

Fixes #61180

Change-Id: Ic0e5f519863d96a139fada08aefb1bcdf4c7a9a3
Reviewed-on: https://go-review.googlesource.com/c/go/+/508135


Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Eli Bendersky <eliben@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>