Parachains. Transcript chellenge bytes

[iceseer]

1. Added Transcript::challenge_bytes.

[codecov]

Codecov Report

Merging #1399 (1f5948a) into master (d4505e2) will increase coverage by 0.13%.
The diff coverage is 6.86%.

❗ Current head 1f5948a differs from pull request most recent head bcd9218. Consider uploading reports for the commit bcd9218 to get more accurate results

@@            Coverage Diff             @@
##           master    #1399      +/-   ##
==========================================
+ Coverage   24.33%   24.46%   +0.13%     
==========================================
  Files         643      633      -10     
  Lines       24252    23723     -529     
  Branches    12573    12344     -229     
==========================================
- Hits         5901     5805      -96     
+ Misses      13085    12641     -444     
- Partials     5266     5277      +11     

Impacted Files	Coverage Δ
core/blockchain/impl/block_tree_impl.hpp	33.33% <ø> (-66.67%)	⬇️
core/common/visitor.hpp	58.33% <0.00%> (ø)
core/injector/application_injector.cpp	32.32% <0.00%> (-7.47%)	⬇️
core/network/impl/peer_view.cpp	0.00% <0.00%> (-3.64%)	⬇️
core/network/peer_view.hpp	0.00% <0.00%> (-100.00%)	⬇️
core/network/types/collator_messages.hpp	0.00% <0.00%> (ø)
core/parachain/thread_pool.hpp	0.00% <0.00%> (ø)
core/primitives/math.hpp	100.00% <ø> (ø)
core/blockchain/impl/block_tree_impl.cpp	21.47% <50.00%> (+1.67%)	⬆️
core/primitives/transcript.hpp	72.72% <100.00%> (ø)
... and 117 more

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