internal/worker: query results by job_id and print success message

Previously, attempting to obtain ejobs results would return a broad
results based on the analyzer binary. This has changed to be more
specific based on job_id, which will greatly reduce the time required to
complete the query. Running the following `ejobs -env=dev results -o
test.json <job-id>` should no longer hang.

Updates golang/go#77925

Change-Id: I05de364208a14059ecab1e3b1bd008aeec2700e3
Reviewed-on: https://go-review.googlesource.com/c/pkgsite-metrics/+/793140
Auto-Submit: Ethan Lee <ethanalee@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>