feat: Alias level critical as fatal

[bruno-garcia]

Following getsentry/sentry-docs#835

[codecov-io]

Codecov Report

Merging #182 into master will decrease coverage by <.01%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master     #182      +/-   ##
==========================================
- Coverage   64.65%   64.65%   -0.01%     
==========================================
  Files          83       83              
  Lines        8994     8996       +2     
==========================================
+ Hits         5815     5816       +1     
- Misses       3179     3180       +1

Impacted Files	Coverage Δ
general/src/protocol/types.rs	74.6% <66.66%> (-0.16%)	⬇️

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