Add IdentifierSet.ToOrderedSlice and ToSlice benchmarks

This will be useful later on when implementing the performance
improvements to compare how much we gain.

Signed-off-by: Leandro López <leandro.lopez@grafana.com>

ast/util_test.go

@@ -0,0 +1,64 @@
+package ast
+
+import (
+	"fmt"
+	"testing"
+)
+
+func testIdentifiers(n int) Identifiers {
+	var is []Identifier
+	for i := 0; i < n; i++ {
+		is = append(is, Identifier(fmt.Sprintf("id-%06d", i)))
+	}
+	return Identifiers(is)
+}
+
+var results []Identifier
+
+func BenchmarkToOrderedSlice(b *testing.B) {
+	tests := []Identifiers{
+		testIdentifiers(1),
+		testIdentifiers(10),
+		testIdentifiers(100),
+		testIdentifiers(1000),
+		testIdentifiers(10000),
+		testIdentifiers(100000),
+	}
+
+	for _, t := range tests {
+		is := IdentifierSet{}
+		is.AddIdentifiers(t)
+
+		b.Run(fmt.Sprintf("%d unique identifiers", len(t)), func(b *testing.B) {
+			var r []Identifier
+			for i := 0; i < b.N; i++ {
+				r = is.ToOrderedSlice()
+			}
+			results = r
+		})
+	}
+}
+
+func BenchmarkToSlice(b *testing.B) {
+	tests := []Identifiers{
+		testIdentifiers(1),
+		testIdentifiers(10),
+		testIdentifiers(100),
+		testIdentifiers(1000),
+		testIdentifiers(10000),
+		testIdentifiers(100000),
+	}
+
+	for _, t := range tests {
+		is := IdentifierSet{}
+		is.AddIdentifiers(t)
+
+		b.Run(fmt.Sprintf("%d unique identifiers", len(t)), func(b *testing.B) {
+			var r []Identifier
+			for i := 0; i < b.N; i++ {
+				r = is.ToSlice()
+			}
+			results = r
+		})
+	}
+}