internal/trace: emit final sync event for generation in Go 1.26+
CL 693398 returned the error from reading a generation immediately, but
this is wrong -- a Sync event must be emitted to indicate the end of the
trace before reporting the error. This caused TestCrashWhileTracing
to fail because that test has a high likelihood of producing a truncated
trace, and it expects at least 2 Sync events. The truncated trace error
would be reported before the second Sync event, which is incorrect.
Fixes #75045.
Change-Id: Ia71592c4ec56a544afc85cdb7b575e143f80e048
Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest
Reviewed-on: https://go-review.googlesource.com/c/go/+/696436 Reviewed-by: Carlos Amedee <carlos@golang.org>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>