feat(exp): add sliceutil package (#489)

- Add a Batches utility to split slices into batches.

hcloud/exp/kit/sliceutil/slice.go

@@ -0,0 +1,9 @@
+package sliceutil
+
+// Batches splits a slice into multiple batches of a desired size.
+func Batches[T any](all []T, size int) (batches [][]T) {
+	for size < len(all) {
+		all, batches = all[size:], append(batches, all[:size])
+	}
+	return append(batches, all)
+}

hcloud/exp/kit/sliceutil/slice_test.go

@@ -0,0 +1,17 @@
+package sliceutil
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBatches(t *testing.T) {
+	all := []int{1, 2, 3, 4, 5}
+	batches := Batches(all, 2)
+
+	assert.Len(t, batches, 3)
+	assert.Equal(t, []int{1, 2}, batches[0])
+	assert.Equal(t, []int{3, 4}, batches[1])
+	assert.Equal(t, []int{5}, batches[2])
+}