Add new annotation for Chisel Circuit serialization (#1580)

ChiselCircuitAnnotation no longer extends CustomFileEmission, rather it
is Unserializable. Also the --chisel-output-file is added to the
ChiselCli.

New phase AddSerializationAnnotations constructs a
CircuitSerializationAnnotation from ChiselCircuitAnnotation and
ChiselOutputFileAnnotation. Both .fir and .pb file formats are
supported. Default format is .fir unless a --chisel-output-file is
specified with a .pb extension.