Add automatic retry for some upload failures

If there are not enough reachable storage servers, try again. Usually the client node will manage to connect to some more eventually.

Created by: codecov[bot]

Codecov Report

Merging #304 (a38264f6) into main (6a517a5f) will increase coverage by 0.06%. The diff coverage is 92.72%.

@@            Coverage Diff             @@
##             main     #304      +/-   ##
==========================================
+ Coverage   91.60%   91.66%   +0.06%     
==========================================
  Files          55       55              
  Lines        5050     5101      +51     
  Branches      689      698       +9     
==========================================
+ Hits         4626     4676      +50     
  Misses        371      371              
- Partials       53       54       +1     

Impacted Files	Coverage Δ
src/_zkapauthorizer/tahoe.py	86.36% <88.00%> (+10.17%)
src/_zkapauthorizer/tests/test_tahoe.py	97.16% <96.66%> (-0.19%)
src/_zkapauthorizer/tests/test_model.py	93.77% <0.00%> (+0.36%)

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