Fix error reporting when trace data is not included (#7136)

This is a 2-part change which required an update to the gateway runtime
as well. Related PR:
apollographql/federation#2242

It was brought to our attention that trace information w.r.t. subgraph
errors is incorrect in the case that there is no trace in the subgraph
response (i.e. no ftv1 support in the subgraph or
`fieldLevelInstrumentation` is 0 or returns 0).

With this change:
* Errors reported by subgraphs (with no trace data in the response) are
now accurately reflected in the numeric error stats
* Operations that receive errors from subgraphs (with no trace data in
the response) are no longer sent as incomplete, error-less traces

The gateway change now collects errors separately when no trace data is
found and passes that error information (subgraph and error path) along
with the other metrics data for the plugin to consume. The plugin uses
the subgraph name and error path in order to add error stat information
to the tree.

In order to make use of this fix, you must be using the latest gateway patch
`@apollo/gateway@2.3.1` in tandem with this change.
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.changeset/heavy-poets-wink.md

@@ -0,0 +1,9 @@
+---
+'@apollo/server': patch
+---
+
+Errors reported by subgraphs (with no trace data in the response) are now accurately reflected in the numeric error stats.
+
+Operations that receive errors from subgraphs (with no trace data in the response) are no longer sent as incomplete, error-less traces.
+
+Note: in order for this fix to take effect, your `@apollo/gateway` version must be updated to v2.3.1 or later.