Log Telegram outages once in plain words

A Telegram outage logs one line at its start and one at its end, with
its length, and the retries between them log nothing. Each line says
first what the user loses or gets, such as "cannot get messages from
Telegram" or "replies go to Telegram again, after 1m25s", and then the
cause in plain words, such as "no answer in 1m10s" or "Telegram answered
502 Bad Gateway".

The errors of the Bot API client hold no method name and no Go deadline
text, so that the log line can say what the call was for. A refused
format, a dropped reply, and an ignored message use the same plain
words.

Issue: e4acfcb