core/state/snapshot: replace diffToDisk ideal batch size with 64MB

[ucwong]

No description provided.

[codecov]

Codecov Report

Merging #1699 (9898ace) into master (29a26eb) will increase coverage by 0.02%.
Report is 16 commits behind head on master.
The diff coverage is 20.51%.

❗ Current head 9898ace differs from pull request most recent head 364f1b6. Consider uploading reports for the commit 364f1b6 to get more accurate results

@@            Coverage Diff             @@
##           master    #1699      +/-   ##
==========================================
+ Coverage   52.53%   52.55%   +0.02%     
==========================================
  Files         481      481              
  Lines       60284    60301      +17     
==========================================
+ Hits        31671    31694      +23     
+ Misses      26194    26190       -4     
+ Partials     2419     2417       -2     

Files Changed	Coverage Δ
cmd/utils/flags.go	1.83% <0.00%> (-0.02%)	⬇️
core/rawdb/accessors_chain.go	43.81% <0.00%> (ø)
core/rawdb/accessors_sync.go	0.00% <0.00%> (ø)
core/rawdb/database.go	9.49% <0.00%> (ø)
core/rawdb/databases_64bit.go	0.00% <0.00%> (ø)
core/state/iterator.go	0.00% <0.00%> (ø)
core/state/snapshot/snapshot.go	40.94% <0.00%> (ø)
core/state/sync.go	0.00% <0.00%> (ø)
core/vm/runtime/runtime.go	75.64% <ø> (ø)
p2p/discover/v4wire/v4wire.go	28.23% <ø> (ø)
... and 4 more

... and 18 files with indirect coverage changes