[#8] hrw: Do not allocate for swap()/less() helpers

```
goos: linux
goarch: amd64
pkg: git.frostfs.info/TrueCloudLab/hrw
cpu: 11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz
                                         │      4      │                  5                  │
                                         │   sec/op    │   sec/op     vs base                │
SortHashersByValue_Typed_fnv_10-8          309.2n ± 2%   294.4n ± 1%   -4.75% (p=0.000 n=10)
SortHashersByValue_Typed_fnv_100-8         2.306µ ± 1%   2.549µ ± 1%  +10.54% (p=0.000 n=10)
SortHashersByValue_Typed_fnv_1000-8        21.73µ ± 1%   24.80µ ± 3%  +14.14% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_10-8     347.1n ± 1%   334.8n ± 2%   -3.56% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_100-8    2.668µ ± 1%   2.954µ ± 3%  +10.72% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_1000-8   2.673µ ± 1%   2.957µ ± 4%  +10.63% (p=0.000 n=10)
geomean                                    1.836µ        1.947µ        +6.01%

                                         │      4       │                  5                   │
                                         │     B/op     │     B/op      vs base                │
SortHashersByValue_Typed_fnv_10-8            216.0 ± 0%     144.0 ± 0%  -33.33% (p=0.000 n=10)
SortHashersByValue_Typed_fnv_100-8          1032.0 ± 0%     960.0 ± 0%   -6.98% (p=0.000 n=10)
SortHashersByValue_Typed_fnv_1000-8        8.133Ki ± 0%   8.062Ki ± 0%   -0.86% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_10-8       216.0 ± 0%     144.0 ± 0%  -33.33% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_100-8     1032.0 ± 0%     960.0 ± 0%   -6.98% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_1000-8    1032.0 ± 0%     960.0 ± 0%   -6.98% (p=0.000 n=10)
geomean                                      867.8          730.1       -15.87%

                                         │     4      │                 5                  │
                                         │ allocs/op  │ allocs/op   vs base                │
SortHashersByValue_Typed_fnv_10-8          4.000 ± 0%   2.000 ± 0%  -50.00% (p=0.000 n=10)
SortHashersByValue_Typed_fnv_100-8         4.000 ± 0%   2.000 ± 0%  -50.00% (p=0.000 n=10)
SortHashersByValue_Typed_fnv_1000-8        4.000 ± 0%   2.000 ± 0%  -50.00% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_10-8     4.000 ± 0%   2.000 ± 0%  -50.00% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_100-8    4.000 ± 0%   2.000 ± 0%  -50.00% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_1000-8   4.000 ± 0%   2.000 ± 0%  -50.00% (p=0.000 n=10)
geomean                                    4.000        2.000       -50.00%
```

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

hrw.go

@@ -21,6 +21,12 @@ type (
 		less func(i, j int) bool
 		swap func(i, j int)
 	}
+
+	hasherSorter[T Hasher, N interface{ ~uint64 | ~float64 }] struct {
+		slice []T
+		dist  []N
+		asc   bool
+	}
 )
 
 // Boundaries of valid normalized weights
@@ -33,6 +39,18 @@ func (s *sorter) Len() int           { return s.l }
 func (s *sorter) Less(i, j int) bool { return s.less(i, j) }
 func (s *sorter) Swap(i, j int)      { s.swap(i, j) }
 
+func (s *hasherSorter[T, N]) Len() int { return len(s.slice) }
+func (s *hasherSorter[T, N]) Less(i, j int) bool {
+	if s.asc {
+		return s.dist[i] < s.dist[j]
+	}
+	return s.dist[i] > s.dist[j]
+}
+func (s *hasherSorter[T, N]) Swap(i, j int) {
+	s.slice[i], s.slice[j] = s.slice[j], s.slice[i]
+	s.dist[i], s.dist[j] = s.dist[j], s.dist[i]
+}
+
 func distance(x uint64, y uint64) uint64 {
 	acc := x ^ y
 	// here used mmh3 64 bit finalizer
@@ -128,29 +146,19 @@ func SortHasherSliceByWeightValue[T Hasher](slice []T, weights []float64, hash u
 		dist[i] = float64(^uint64(0)-d) * weights[i]
 	}
 
-	sort.Sort(&sorter{
+	sort.Sort(&hasherSorter[T, float64]{
-		l: len(slice),
+		slice: slice,
-		swap: func(i, j int) {
+		dist:  dist,
-			slice[i], slice[j] = slice[j], slice[i]
+		asc:   false,
-			dist[i], dist[j] = dist[j], dist[i]
-		},
-		less: func(i, j int) bool {
-			return dist[i] > dist[j] // higher distance must be placed lower to be first
-		},
 	})
 }
 
 // sortHasherByDistance is similar to sortByDistance but accepts slice directly.
 func sortHasherByDistance[T Hasher](slice []T, byIndex bool, dist []uint64) {
-	sort.Sort(&sorter{
+	sort.Sort(&hasherSorter[T, uint64]{
-		l: len(slice),
+		slice: slice,
-		swap: func(i, j int) {
+		dist:  dist,
-			slice[i], slice[j] = slice[j], slice[i]
+		asc:   true,
-			dist[i], dist[j] = dist[j], dist[i]
-		},
-		less: func(i, j int) bool {
-			return dist[i] < dist[j]
-		},
 	})
 }