Allow multiple packet_numbers in frames_processed

[rmarx]

Currently, frames_processed only allows indicating a single packet_number.

However, discussion in #163 has shown that you might want to aggregate frames across multiple packets for some use cases, so it makes sense to make this into an Array<uint64> instead.

[kuroa-me]

About this structure

frames_processed : 
{
       frames:Array<QuicFrame>,
       packet_numbers?:Array<uint64>
}

How do we log the packet_numbers when we have multiple frames in one packet? My suggestion is we log them one to one.

Example (suppose fr1 and fr2 are in the same packet):

{
       frames:[fr1, fr2, fr3, fr4],
       packet_number:[1, 1, 2, 3]
}

This way we don't have to do any search when the packets arrive out of order.

[rmarx]

Good point and your suggestion seems sensible :)