v0.8.1

Say which provider boot is being waited on

Boot is a sequence of blocking steps that log nothing until they finish, so
a slow one shows up as a gap with the next unrelated line at the end of it —
and that line takes the blame. Each provider now names itself on the way in
and reports what it cost on the way out.

Debug level, and the name is in the message rather than a field, so it reads
the same through a journal that drops structured fields.