Support data size length longer than 9 digits in binblockread

[ChaoticEnigma]

While working on a RIGOL MHO900/98 instrument class, I found that reading waveform data with a size larger than 9 digits (e.g. 500M points * 2 bytes) will encode the length of the data size in base-16. This change allowed me to read the full waveform data, although it was VERY slow on this scope.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.20%. Comparing base (0e26865) to head (6751b8f).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #466   +/-   ##
=======================================
  Coverage   99.20%   99.20%           
=======================================
  Files          96       96           
  Lines        9648     9648           
=======================================
  Hits         9571     9571           
  Misses         77       77           

Flag	Coverage Δ
unittests	99.20% <100.00%> (ø)

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[scasagrande]

awesome! thanks!!