tpl/collections: Use MapRange() in Where

Speeds up execution when the collection is a map:

```
            │ stash.bench │         fix-mapkeys.bench          │
            │   sec/op    │   sec/op     vs base               │
WhereMap-10   79.35µ ± 1%   61.45µ ± 1%  -22.56% (p=0.002 n=6)

            │ stash.bench  │          fix-mapkeys.bench          │
            │     B/op     │     B/op      vs base               │
WhereMap-10   55.36Ki ± 0%   31.35Ki ± 0%  -43.37% (p=0.002 n=6)

            │ stash.bench │         fix-mapkeys.bench         │
            │  allocs/op  │  allocs/op   vs base              │
WhereMap-10   2.003k ± 0%   2.002k ± 0%  -0.05% (p=0.002 n=6)
```

tpl/collections/where.go

@@ -409,7 +409,6 @@ func (ns *Namespace) checkWhereArray(ctxv, seqv, kv, mv reflect.Value, path []st
 				for i, elemName := range path {
 					var err error
 					vvv, err = evaluateSubElem(ctxv, vvv, elemName)
-
 					if err != nil {
 						continue
 					}
@@ -442,9 +441,10 @@ func (ns *Namespace) checkWhereArray(ctxv, seqv, kv, mv reflect.Value, path []st
 // checkWhereMap handles the where-matching logic when the seqv value is a Map.
 func (ns *Namespace) checkWhereMap(ctxv, seqv, kv, mv reflect.Value, path []string, op string) (any, error) {
 	rv := reflect.MakeMap(seqv.Type())
-	keys := seqv.MapKeys()
-	for _, k := range keys {
-		elemv := seqv.MapIndex(k)
+	iter := seqv.MapRange()
+	for iter.Next() {
+		k := iter.Key()
+		elemv := iter.Value()
 		switch elemv.Kind() {
 		case reflect.Array, reflect.Slice:
 			r, err := ns.checkWhereArray(ctxv, elemv, kv, mv, path, op)

tpl/collections/where_test.go

@@ -902,3 +902,19 @@ func BenchmarkWhereOps(b *testing.B) {
 		}
 	})
 }
+
+func BenchmarkWhereMap(b *testing.B) {
+	ns := newNs()
+	seq := map[string]string{}
+
+	for i := 0; i < 1000; i++ {
+		seq[fmt.Sprintf("key%d", i)] = "value"
+	}
+
+	for i := 0; i < b.N; i++ {
+		_, err := ns.Where(context.Background(), seq, "key", "eq", "value")
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}