refactor: pass Vec<SpanRecord> to Reporter::report() instead of &[SpanRecord]

[andylokandy]

Closes #24

[Xuanwo]

This seems not right

[andylokandy]

It's intended because a span may be consumed multiple times in jaeger udp reporter:

fastrace/fastrace-jaeger/src/lib.rs

Lines 116 to 128 in a6c639c

	let batch_size = spans_per_batch.min(spans.len() - sent_spans);
	let jaeger_spans = self.convert(&spans[sent_spans..sent_spans + batch_size]);
	let bytes = self.serialize(jaeger_spans)?;
	if bytes.len() >= MAX_UDP_PACKAGE_SIZE {
	if batch_size <= 1 {
	sent_spans += 1;
	} else {
	spans_per_batch /= 2;
	}
	continue;
	}
	self.socket.send_to(&bytes, self.agent_addr)?;
	sent_spans += batch_size;