embeddeddb: use executeUpdate instead of executeQuery for truncate statement

This is required for more recent versions of the MySQL JDBC driver, as well as H2.

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>
jdbi: introduce @SmartFetchSize

Similar to @FetchSize, but encapsulates the magic values for streaming.

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>