BitTorrent client

[canepat]

This PR introduces a simple BitTorrent client based on libtorrent library. It is necessary for downloading and seeding snapshot files used for the Snapshot Sync functionality.

Main changes are:

• add new third-party library libtorrent
• use torrent-rasterbar target in CMake build scripts
• adjust CMake build scripts to include Boost::headers target required by libtorrent
• add BitTorrentClient class with unit tests

Additional changes are required by the usage of BOOST_ASIO_NO_DEPRECATED in libtorrent:

• replace boost::asio::io_context::post with boost::asio::post
• replace boost::asio::io_context::work with boost::asio::executor_work_guard
• replace boost::asio::ip::address::from_string with boost::asio::ip::make_address

[codecov]

Codecov Report

Merging #785 (93d9429) into master (d72e0cc) will increase coverage by 0.05%.
The diff coverage is 73.00%.

@@            Coverage Diff             @@
##           master     #785      +/-   ##
==========================================
+ Coverage   74.97%   75.02%   +0.05%     
==========================================
  Files         196      197       +1     
  Lines       14180    14379     +199     
  Branches     2225     2285      +60     
==========================================
+ Hits        10631    10788     +157     
- Misses       2607     2618      +11     
- Partials      942      973      +31     

Impacted Files	Coverage Δ
node/silkworm/snapshot/bittorrent.cpp	72.86% <72.86%> (ø)
node/silkworm/rpc/completion_end_point.cpp	88.37% <100.00%> (-2.33%)	⬇️
node/silkworm/rpc/server/server_context_pool.cpp	60.16% <0.00%> (-0.82%)	⬇️
core/silkworm/execution/evm.cpp	93.84% <0.00%> (-0.25%)	⬇️
core/silkworm/types/transaction.cpp	82.10% <0.00%> (+0.31%)	⬆️
core/silkworm/trie/hash_builder.cpp	98.60% <0.00%> (+0.46%)	⬆️
core/silkworm/types/block.cpp	87.50% <0.00%> (+0.50%)	⬆️
core/silkworm/state/in_memory_state.cpp	92.70% <0.00%> (+0.52%)	⬆️
core/silkworm/consensus/blockchain.cpp	88.70% <0.00%> (+0.80%)	⬆️
... and 4 more

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