Clean up throttler table more aggressively

First commit:

winery: add indexes on the updated column of the throttler tables

All throttler queries filter these tables using ranges of the updated
column, so adding a block range index makes these queries much more
efficient.

Ref. swh/infra/sysadm-environment#5388

Second commit:

winery: clean up the throttler tables more aggressively

Make the throttler window of measurement a module-level constant, and
clean up stale rows that are twice as old as the window (10 minutes)
instead of one month old.

Ref. swh/infra/sysadm-environment#5388 (closed)