Vacuum - duration per table

[aleszeleny]

Hello, could we add a report to vacuums that will (as a table is enough) the total time spent on vacuums per relation?

Motivation:

• increased vacuum activity can already be easily recognized
• the number of vacuums is high, but there are small frequently updated -> vacuumed as well as there are some big tables

Having time reports spent on vacuuming a relation might help to understand what table consumes the most resources on vacuuming easily.