[RNTuple] fix multi page reading for Index32/Index64 columns

[Moelf]

fix #312

see:

• [RNTuple] Wrong offset Index32/Index64 array when read from multiple pages #312

for detailed investigation

[codecov]

Codecov Report

Attention: Patch coverage is 68.18182% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 86.16%. Comparing base (a96f21e) to head (c7dfdef).

Files	Patch %	Lines
src/RNTuple/fieldcolumn_reading.jl	12.50%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #315      +/-   ##
==========================================
- Coverage   86.40%   86.16%   -0.25%     
==========================================
  Files          18       18              
  Lines        2450     2458       +8     
==========================================
+ Hits         2117     2118       +1     
- Misses        333      340       +7     

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[tamasgal]

Looks good to me, so far I can tell ;)

[tamasgal]

These comparisons look a bit weird but it is what it is ;) If we do such checks at more places in future, we should probably extract that or do some dispatch magic.

[Moelf]

true, and we have like 3 different such ifelse right now.

poly-Decompression is hard