HadoopFormatIO should allow to specify coders

HadoopFormatIO does allow only to pass in type descriptors for key and value and those are then resolved to Coder via CoderRegistry.

We did find this restrictive after https://issues.apache.org/jira/browse/BEAM-9569
which makes it impossible to emit Row out of the source.

Easy solution I see can be to allow set Coder directly and bypass the resolution against registry in that case.