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/insert.go

@@ -10,6 +10,8 @@ package qb
 import (
 	"bytes"
 	"time"
+
+	"github.com/scylladb/gocqlx/v2"
 )
 
 // initializer specifies an value for a column in an insert operation.
@@ -78,6 +80,11 @@ func (b *InsertBuilder) ToCql() (stmt string, names []string) {
 	return
 }
 
+// Query returns query built on top of current InsertBuilder state.
+func (b *InsertBuilder) Query(session gocqlx.Session) *gocqlx.Queryx {
+	return session.Query(b.ToCql())
+}
+
 // Into sets the INTO clause of the query.
 func (b *InsertBuilder) Into(table string) *InsertBuilder {
 	b.table = table