core/bloombits: use atomic type

[ucwong]

No description provided.

[codecov]

Codecov Report

Merging #1470 (5448cab) into master (3cb51d9) will increase coverage by 0.49%.
The diff coverage is 16.66%.

❗ Current head 5448cab differs from pull request most recent head cc84caa. Consider uploading reports for the commit cc84caa to get more accurate results

@@            Coverage Diff             @@
##           master    #1470      +/-   ##
==========================================
+ Coverage   51.71%   52.20%   +0.49%     
==========================================
  Files         473      473              
  Lines       59358    59358              
==========================================
+ Hits        30696    30988     +292     
+ Misses      26307    26018     -289     
+ Partials     2355     2352       -3     

Impacted Files	Coverage Δ
core/vm/cvm.go	17.24% <0.00%> (ø)
core/vm/instructions.go	20.13% <0.00%> (ø)
params/version.go	33.33% <ø> (ø)
core/bloombits/matcher.go	95.77% <50.00%> (+95.77%)	⬆️

... and 14 files with indirect coverage changes