Do not panic when blob does not have all pieces yet

[adzialocha]

This PR fixes a race condition where nodes would sometimes crash when they attempted to materialise a blob where not all pieces are in the database yet (for example during replication). This was solved by:

1. Not failing critically on this error
2. Moving the check if all pieces are given right at the beginning of the method

Closes #562

📋 Checklist

• Add tests that cover your changes
• Add this PR to the Unreleased section in CHANGELOG.md
• Link this PR to any issues it closes
• New files contain a SPDX license header

[codecov]

Codecov Report

Patch coverage: 64.81% and project coverage change: -0.68% ⚠️

Comparison is base (966774a) 92.35% compared to head (f773516) 91.67%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #563      +/-   ##
==========================================
- Coverage   92.35%   91.67%   -0.68%     
==========================================
  Files         106      106              
  Lines       17835    17980     +145     
==========================================
+ Hits        16471    16484      +13     
- Misses       1364     1496     +132     

Files Changed	Coverage Δ
aquadoggo/src/db/errors.rs	0.00% <ø> (ø)
aquadoggo/src/materializer/tasks/blob.rs	46.25% <18.18%> (-12.22%)	⬇️
aquadoggo/src/db/stores/blob.rs	79.49% <76.74%> (-18.90%)	⬇️

... and 2 files with indirect coverage changes

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