sentry: RLPx handshake framing and Hello message

[battlmonstr]

• framing: secrets, MAC, encrypt/decrypt frames and messages
• Hello message exchange

Refactorings:

• rename session keys to auth keys
• refactor ECIES crypto to reuse in framing
• refactor AES to support more modes for framing

[codecov[bot]]

Codecov Report

Merging #741 (af4e81e) into master (4f2c788) will decrease coverage by 0.03%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #741      +/-   ##
==========================================
- Coverage   76.25%   76.21%   -0.04%     
==========================================
  Files         190      190              
  Lines       13052    13052              
  Branches     2118     2118              
==========================================
- Hits         9953     9948       -5     
+ Misses       2211     2210       -1     
- Partials      888      894       +6     

Impacted Files	Coverage Δ
node/silkworm/rpc/completion_end_point.cpp	86.04% <0.00%> (-9.31%)	:arrow_down:
core/silkworm/common/util.cpp	99.37% <0.00%> (-0.63%)	:arrow_down:
core/silkworm/types/transaction.cpp	81.78% <0.00%> (-0.32%)	:arrow_down:
core/silkworm/execution/evm.cpp	93.85% <0.00%> (ø)
node/silkworm/rpc/server/server_context_pool.cpp	60.97% <0.00%> (+0.81%)	:arrow_up:

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[AndreaLanfranchi]

@canepat I'd add a comment to remove stbrume's keccak function when/if @chfast implements a rolling keccak into ethash library. Having two different implementations can be confusing.

[canepat]

@canepat I'd add a comment to remove stbrume's keccak function when/if @chfast implements a rolling keccak into ethash library. Having two different implementations can be confusing.

Good point, @battlmonstr can you please add such comment in next PR?