This removes the "title" argument to `trace.New()`. This was previously
only displayed as an attribute on the span, which is confusing since
people would often use a span name for this argument since it is called
"title." OpenTelemetry does not have the concept of a family and title
(these are from `x/net/trace`, which is no longer used), so this is
another step towards reconciling our tracing package with OpenTelemetry.
Basically, I went through all uses of `trace.New()` and either named the
span `family.title`, removed the title in the case it was an empty
string, or converted the title to a set of more structured attributes.
Now, `trace.New()` only takes a context, a span name, and an optional
set of attributes.
cf037e2ee4