QA/v1: Run the vote extensions test

[hvanz]

• Run the vote-extension test as described in RELEASES.md and docs/reference/qa/method.md to measure the impact of vote extensions on performance.
• Compare the obtained results with those of v0.38
• Write the corresponding section in the final QA report for v1.x

[hvanz]

Won't do for v1 as this was a one-shot test instance for the QA process of v0.38, the version on which vote extensions were first included. Also, v1 does not have any significant change to vote extensions.