support more than 7 levels in metrics

[ucwong]

No description provided.

[codecov]

Codecov Report

Merging #1674 (d89c9f3) into master (10544b7) will decrease coverage by 0.04%.
Report is 4 commits behind head on master.
The diff coverage is 73.91%.

❗ Current head d89c9f3 differs from pull request most recent head 14e5dc4. Consider uploading reports for the commit 14e5dc4 to get more accurate results

@@            Coverage Diff             @@
##           master    #1674      +/-   ##
==========================================
- Coverage   52.63%   52.59%   -0.04%     
==========================================
  Files         481      481              
  Lines       60239    60238       -1     
==========================================
- Hits        31705    31684      -21     
- Misses      26122    26137      +15     
- Partials     2412     2417       +5     

Files Changed	Coverage Δ
core/rawdb/accessors_chain.go	43.81% <0.00%> (ø)
ctxc/api_backend.go	0.00% <0.00%> (ø)
ctxcdb/leveldb/leveldb.go	23.38% <0.00%> (ø)
ctxc/filters/filter.go	62.17% <100.00%> (-0.17%)	⬇️

... and 14 files with indirect coverage changes