fix: fetch cves from mirror not working

[b31ngd3v]

fetch from mirror was not working due to recent changes in the db structure (two tables were added cve_metrics and metrics)

[codecov-commenter]

Codecov Report

Merging #3122 (72ac3bd) into main (c503c22) will decrease coverage by 1.32%.
The diff coverage is 90.90%.

@@            Coverage Diff             @@
##             main    #3122      +/-   ##
==========================================
- Coverage   83.17%   81.85%   -1.32%     
==========================================
  Files         716      716              
  Lines       11050    11051       +1     
  Branches     1481     1482       +1     
==========================================
- Hits         9191     9046     -145     
- Misses       1466     1621     +155     
+ Partials      393      384       -9     

Flag	Coverage Δ
longtests	81.32% <90.90%> (-0.28%)	⬇️
win-longtests	79.46% <90.90%> (-1.26%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
cve_bin_tool/cvedb.py	66.17% <90.00%> (-0.86%)	⬇️
cve_bin_tool/fetch_json_db.py	48.90% <100.00%> (ø)

... and 7 files with indirect coverage changes

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[terriko]

I feel like there's got to be a more elegant way to handle the year_breakdown stuff, or that we at least need some comments explaining what the expected cases actually mean (I know, there wasn't one before, but part of the fun of code review is that we can use it to encourage refactoring anytime!).

In the interest of getting the mirror fetch working again, I'm going to merge this as is and open a separate issue. suggesting we explain what those cases mean.