perf: replace sort.Slice with slices.SortFunc

Since we're already requiring the slices package in stdlib with this
refactor, we can utilize this newer function which should be slightly
more efficient (and has nicer ergonomics imo).

Performs roughly ~11% faster during NewChooser initialization.

goos: darwin
goarch: arm64
pkg: github.com/mroth/weightedrand/v2
                        │  v3-dev1.txt  │             v3-dev2.txt              │
                        │    sec/op     │   sec/op     vs base                 │
NewChooser/size=1e1-8     132.90n ±  0%   70.73n ± 1%  -46.78% (p=0.002 n=6)
NewChooser/size=1e2-8      472.8n ±  0%   444.1n ± 2%   -6.05% (p=0.002 n=6)
NewChooser/size=1e3-8      3.412µ ±  0%   3.333µ ± 0%   -2.30% (p=0.002 n=6)
NewChooser/size=1e4-8      31.03µ ±  0%   30.30µ ± 0%   -2.33% (p=0.002 n=6)
NewChooser/size=1e5-8      295.9µ ±  0%   291.9µ ± 1%   -1.36% (p=0.002 n=6)
NewChooser/size=1e6-8      2.843m ±  1%   2.775m ± 1%   -2.37% (p=0.002 n=6)
NewChooser/size=1e7-8      35.92m ±  1%   32.99m ± 2%   -8.16% (p=0.002 n=6)
geomean                    279.7n         36.41µ       -11.60%               ¹
¹ benchmark set differs from baseline; geomeans may not be comparable

weightedrand.go

@@ -9,11 +9,11 @@
 package weightedrand
 
 import (
+ "cmp"
  "errors"
  "math"
  "math/rand/v2"
  "slices"
- "sort"
 )
 
 // Choice is a generic wrapper that can be used to add weights for any item.
@@ -41,8 +41,8 @@ type Chooser[T any, W integer] struct {
 
 // NewChooser initializes a new Chooser for picking from the provided choices.
 func NewChooser[T any, W integer](choices ...Choice[T, W]) (*Chooser[T, W], error) {
- sort.Slice(choices, func(i, j int) bool {
- return choices[i].Weight < choices[j].Weight
+ slices.SortFunc(choices, func(a, b Choice[T, W]) int {
+ return cmp.Compare(a.Weight, b.Weight)
  })
 
  totals := make([]uint64, len(choices))
@@ -67,7 +67,6 @@ func NewChooser[T any, W integer](choices ...Choice[T, W]) (*Chooser[T, W], erro
  return &Chooser[T, W]{data: choices, totals: totals, max: runningTotal}, nil
 }
 
-
 // Possible errors returned by NewChooser, preventing the creation of a Chooser
 // with unsafe runtime states.
 var (