Fix some performance related issues

[ashamis]

• big request table will use an intrusive linked list so when an item is removed it can be done in O(1)
• the checkpoint in pbft is now only used for marking stable and therefore does not need to be signed
• the request queue will now have a queue per thread. This allows us to maintain session consistency while ensuring that we have enough work for all execution threads
• bring the intrusive double linked list from snmalloc
• print a request time series (second granularity) when collecting other metrics

[codecov-io]

Codecov Report

Merging #940 into master will decrease coverage by 0.54%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master     #940      +/-   ##
==========================================
- Coverage   68.96%   68.43%   -0.54%     
==========================================
  Files         100      101       +1     
  Lines        7820     7978     +158     
==========================================
+ Hits         5393     5459      +66     
- Misses       2427     2519      +92     

Flag	Coverage Δ
#unit_BFT	68.43% <50.00%> (-0.54%)	⬇️
#unit_CFT	68.43% <50.00%> (-0.54%)	⬇️

Impacted Files	Coverage Δ
src/node/genesisgen.h	49.26% <0.00%> (-2.67%)	⬇️
src/node/ledgersecrets.h	14.67% <0.00%> (-0.40%)	⬇️
src/node/networkstate.h	100.00% <ø> (ø)
src/node/rpc/metrics.h	0.00% <0.00%> (ø)
src/node/values.h	80.00% <ø> (ø)
src/node/rpc/memberfrontend.h	60.53% <16.22%> (-7.24%)	⬇️
src/node/networkencryption.h	33.33% <33.33%> (ø)
src/tls/25519.h	83.67% <83.67%> (+6.75%)	⬆️
src/node/rpc/nodecalltypes.h	100.00% <100.00%> (ø)
src/node/rpc/nodefrontend.h	78.65% <100.00%> (ø)
... and 3 more

[ghost]

adding_things@5895 aka 20200311.9 vs master ewma over 30 builds from 5534 to 5893