Previously, `QueryJobInfo` was composed of two parts: a `QueryInfo` and
a `QueryJob`. However, both `QueryInfo` and `QueryJob` have a `span`
field, which seem to be the same. So, the `span` was recorded twice.

Now, `QueryJobInfo` is composed of a `QueryStackFrame` (the other field
of `QueryInfo`) and a `QueryJob`. So, now, the `span` is only recorded
once.