feat (pytket-encoder): Track circuit information on circuit boxes, and re-enable nested DFG encoding

[aborgna-q]

tket2/tket/src/serialize/pytket/encoder.rs

Lines 912 to 920 in e648ad1

	// TODO: DFG and function call emissions are temporarily disabled,
	// since we cannot track additional metadata associated with the
	// nested circuit in a `CircuitBox` as we'd do for the root one in
	// [`EncodedCircuitInfo`].
	//
	// See the `unsupported_extras_in_circ_box` case in
	// `tests::encoded_circuit_roundtrip` for a failing case when this
	// is enabled.
	/*