Validator: Store and record change to stake

[Geod24]

Currently, changes to stake are indirectly recorded and handshake may start
to return different result any time. With this change, we ensure that we
have a single point from which changes are performed, and tracked.

@omerfirmak : This was my foray into #2868 as well as vibe-d/vibe.d#2638 and vibe-d/vibe.d#2637 (with the underlying rationale that I wanted to break down vibe.web.rest : request so we could re-use it in an override of RestInterfaceClient.request).

If this doesn't make sense, feel free to close.

[codecov]

Codecov Report

Merging #2877 (1bdc372) into v0.x.x (f027f34) will decrease coverage by 0.14%.
The diff coverage is 81.25%.

@@            Coverage Diff             @@
##           v0.x.x    #2877      +/-   ##
==========================================
- Coverage   79.17%   79.03%   -0.15%     
==========================================
  Files         207      207              
  Lines       18168    18180      +12     
==========================================
- Hits        14385    14368      -17     
- Misses       3783     3812      +29     

Flag	Coverage Δ
integration	21.26% <ø> (+0.21%)	⬆️
unittests	87.28% <81.25%> (-0.20%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
source/agora/node/Validator.d	92.57% <81.25%> (-1.30%)	⬇️
source/agora/consensus/BlockStorage.d	68.90% <0.00%> (-10.61%)	⬇️
source/agora/consensus/protocol/Nominator.d	90.75% <0.00%> (-0.95%)	⬇️
source/agora/consensus/pool/Transaction.d	94.13% <0.00%> (+0.32%)	⬆️
source/agora/node/FullNode.d	72.16% <0.00%> (+0.68%)	⬆️
agora/submodules/ocean/src/ocean/util/log/Logger.d	69.15% <0.00%> (+2.80%)	⬆️
source/agora/test/LocalTransactions.d	91.11% <0.00%> (+4.44%)	⬆️

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[Geod24]

Rebased

[omerfirmak]

Well, the existing implementation was consistent IMO. A validator would always enroll with the stake that it presents in a handshake call. I didnt see the point but I held back reviewing this until I started working on #2868

[omerfirmak]

I believe this introduced a bug

Some nodes are reporting missing peers although they are connected to all 32 nodes, verified thru node_info.

Jan 30 10:42:21 eu-005 agora[2436465]: 2022-01-30 10:42:19,603 Info [agora.network.Manager] - Doing periodic network discovery: 31 required peers requested, 6 missing, known 32