Fix Logger setLevel not resetting other levels

[aminalaee]

Fixes #56

At first I thought it should only reset lower levels, which is a bit less verbose, but it should also reset higher levels:

for example:

logger.setLevel(picologging.INFO)

# This should enable levels ERROR and CRITICAL but also disable DEBUG, INFO, WARNING
logger.setLevel(picologging.ERROR)

[tonybaloney]

see comments

[codecov-commenter]

Codecov Report

Merging #57 (0220afa) into main (7a68c06) will increase coverage by 0.10%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #57      +/-   ##
==========================================
+ Coverage   86.28%   86.39%   +0.10%     
==========================================
  Files          10       10              
  Lines        1881     1896      +15     
==========================================
+ Hits         1623     1638      +15     
  Misses        258      258              

Impacted Files	Coverage Δ
src/picologging/logger.cxx	82.28% <100.00%> (+0.75%)	⬆️

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[tonybaloney]

thanks for the patch!