Updates now retry on failure

[tli2]

Updates were too conservative from before, and immediately return false when compare-and-swap fail on the version chain. The failure could be an innocuous one from the GC. In this PR we changed updates to retry on a CAS failure and only abort after seeing an actual conflict.

[codecov]

Codecov Report

Merging #345 into master will increase coverage by 0.08%.
The diff coverage is 81.25%.

@@            Coverage Diff             @@
##           master     #345      +/-   ##
==========================================
+ Coverage   89.44%   89.52%   +0.08%     
==========================================
  Files         117      117              
  Lines        4376     4374       -2     
==========================================
+ Hits         3914     3916       +2     
+ Misses        462      458       -4

Impacted Files	Coverage Δ
src/storage/data_table.cpp	97.9% <81.25%> (+0.66%)	⬆️
src/transaction/transaction_manager.cpp	94.87% <0%> (+0.85%)	⬆️
src/storage/garbage_collector.cpp	91.3% <0%> (+1.08%)	⬆️
src/network/connection_handle.cpp	52.94% <0%> (+1.96%)	⬆️

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[mbutrovich]

Thanks for the quick fix.