Display buffer duration in EXPLAIN ANALYZE VERBOSE

[sopel39]

Example

Output buffer utilization distribution (%): {p01=0.00, p05=0.00, p10=0.00, p25=0.00, p50=0.00, p75=0.00, p90=0.00, p95=0.00, p99=0.00, max=0.00, duration=6.71s}

[colebow]

Do we want a release note for this?

[sopel39]

Does this need release notes?

This doesn't need a RN.

adding the no-release-notes label, or just writing "no release notes" in the PR description.

Will do!