Fuzz storage proof decoder

[kostko]

Fixes #2637

[codecov]

Codecov Report

Merging #2703 into master will decrease coverage by 0.02%.
The diff coverage is 9.09%.

@@            Coverage Diff             @@
##           master    #2703      +/-   ##
==========================================
- Coverage    63.2%   63.17%   -0.03%     
==========================================
  Files         377      377              
  Lines       35448    35458      +10     
==========================================
- Hits        22404    22401       -3     
- Misses      10244    10246       +2     
- Partials     2800     2811      +11

Impacted Files	Coverage Δ
go/storage/mkvs/urkel/node/node.go	71.2% <0%> (-1.85%)	⬇️
go/storage/mkvs/urkel/syncer/proof.go	83.92% <33.33%> (-1.53%)	⬇️
go/worker/compute/executor/committee/state.go	74.07% <0%> (-11.12%)	⬇️
.../consensus/tendermint/apps/epochtime_mock/state.go	84.61% <0%> (-5.13%)	⬇️
go/runtime/committee/nodes.go	80.64% <0%> (-4.31%)	⬇️
go/worker/storage/service_external.go	47.31% <0%> (-4.31%)	⬇️
go/worker/compute/executor/committee/node.go	62% <0%> (-3.35%)	⬇️
go/storage/mkvs/urkel/lookup.go	72.72% <0%> (-2.28%)	⬇️
go/runtime/tagindexer/tagindexer.go	68.47% <0%> (-2.18%)	⬇️
go/storage/mkvs/urkel/iterator.go	84.37% <0%> (-1.25%)	⬇️
... and 15 more

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