qb: Added shortcuts to Queryx

It allows to write shorter and more straightforward code.
Instead writing:

```
session.Query(qb.Select("cluster").Columns("id").ToCql())
```

you can write:

```
qb.Select("cluster").Columns("id").Query(session)
```

qb/batch.go

@@ -8,6 +8,8 @@ import (
 	"bytes"
 	"fmt"
 	"time"
+
+	"github.com/scylladb/gocqlx/v2"
 )
 
 // BATCH reference:
@@ -64,6 +66,11 @@ func (b *BatchBuilder) ToCql() (stmt string, names []string) {
 	return
 }
 
+// Query returns query built on top of current BatchBuilder state.
+func (b *BatchBuilder) Query(session gocqlx.Session) *gocqlx.Queryx {
+	return session.Query(b.ToCql())
+}
+
 // Add builds the builder and adds the statement to the batch.
 func (b *BatchBuilder) Add(builder Builder) *BatchBuilder {
 	return b.AddStmt(builder.ToCql())