Seastar's on_internal_error() is a useful replacement for assert()
but it's inconvenient that it requires each caller to supply a logger -
which is often inconvenient, especially when the caller is a header file.
So in this patch we introduce a utils::on_internal_error() function
which is the same as seastar::on_internal_error() (the former calls
the latter), except it uses a single logger instead of asking the caller
to pass a logger.
Refs #7871
Signed-off-by: Nadav Har'El <nyh@scylladb.com>