TransportManger: Use a builder pattern for the transport manager

https://github.com/paritytech/litep2p/blob/e0b7118ea2ca3e9f9beb9605f649d7e9dcdd24c4/src/transport/manager/mod.rs#L259-L268

	impl TransportManager {
	/// Create new [`crate::transport::manager::TransportManager`].
	// TODO: don't return handle here
	pub fn new(
	keypair: Keypair,
	supported_transports: HashSet<SupportedTransport>,
	bandwidth_sink: BandwidthSink,
	max_parallel_dials: usize,
	connection_limits_config: limits::ConnectionLimitsConfig,
	) -> (Self, TransportManagerHandle) {

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