ci/govulncheck: fix and simplify the bash script

[Julio-Guerra]

What does this PR do?

Avoid bash script problem (especially due to the previous echo $results | wc -l always returning 1.

Motivation

The bash script is always failing due to a mistake. To avoid it and make this CI more useful, we instead let govulncheck report its exit code along with its detailed output to make this workflow directly usable.

Describe how to test/QA your changes

Reviewer's Checklist

• If known, an appropriate milestone has been selected; otherwise the Triage milestone is set.
• Changed code has unit tests for its functionality.
• If this interacts with the agent in a new way, a system test has been added.

[pr-commenter]

Benchmarks

Comparing candidate commit 324db9e in PR branch julio.guerra/govulncheck-ci-fix-script with baseline commit a2b9399 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 6 cases.