[tools] Update moq_decode.py to support draft-18

[afrind]

I did not read any of this code

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This change is 

[afrind]

Example output from interop:

Decoding 82 bytes (draft-18):
  05 00 4f 10 4c 54 72 61 63 6b 20 2f 6d 6f 71 2d 74 65 73 74 2d 30 30 2f 30 2f 30 2f 30 2f 32 2f 35 2f 35 2f 31 30 32 34 2f 31 30 30 2f 35 30 2f 31 2f 31 2f 30 2f 2d 31 2f 2d 31 2f 30 2f 74 65 73 74 20 64 6f 65 73 20 6e 6f 74 20 65 78 69 73 74 00

  Offset    Bytes                 Field                         Value
  ──────    ─────                 ─────                         ─────
  [0000]  05                    frame_type                    REQUEST_ERROR  (0x5)
  [0001]  00 4f                 frame_length                  79
  [0003]  10                    error_code                    16
  [0004]  4c                    retry_interval_ms             76

  Hex dump:
  0000  05 00 4f 10 4c 54 72 61 63 6b 20 2f 6d 6f 71 2d
                          ^^                           
  0010  74 65 73 74 2d 30 30 2f 30 2f 30 2f 30 2f 32 2f
  0020  35 2f 35 2f 31 30 32 34 2f 31 30 30 2f 35 30 2f
  0030  31 2f 31 2f 30 2f 2d 31 2f 2d 31 2f 30 2f 74 65
  0040  73 74 20 64 6f 65 73 20 6e 6f 74 20 65 78 69 73
  0050  74 00

  ! Error at offset 0x06: underflow reading string of 84 byte(s)

[michalhosna]

I did not read any of this code

[michalhosna]

I did not read any of this code

@michalhosna reviewed 1 file and all commit messages, and made 1 comment.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on akash-a-n, gmarzot, mondain, Oxyd, peterchave, suhasHere, and TimEvens).