Describe the bug
HTTP interface INSERT does not distinguish between EOF and unexpected EOF (connection lost/etc.).
HTTP POST with Content-Length - rows are inserted even if less than Content-Length bytes have been received.
HTTP POST with Transfer-Encoding: chunked - rows are inserted even if zero-length chunk hasn't been received.

This makes it impossible to rely on block deduplication with Replicated*MergeTree because ClickHouse will still form a block (with less rows than intended) even if the connection is lost before receiving all of the data.

How to reproduce
create table values(value Int64) engine = Log()

For chunked encoding:

# send 10 rows per second.
$ (echo 'insert into values format CSV';  seq 100) | pv -lbar -L10 | curl -s  localhost:8123 -X POST -T -
Ctrl-C after few seconds

This will close the connection without sending the last zero-length chunk.
The rows will still be inserted though

Expected behavior
ClickHouse does not insert rows when an unexpected EOF observed

Additional context
Looks like Poco's HTTPChunkedStreamBuf and HTTPFixedLengthStreamBuf just don't handle this.