fix: be adaptive to the log schema changing in inspect-table

[nicklan]

What changes are proposed in this pull request?

We were hard coding the number of expected leaf fields we would get when visiting log data. This meant any changes to the log schema would silently break this example. We already have code to extract the offsets of the getters within the schema, so we should just adapt to changes (although reordering the schema would be bad).

This PR just computes the expected number of getters from the number of leaves in the schema, and ensures that's what we get back from the visitor, instead of hard-coding the number.

How was this change tested?

Run example on existing tables

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.90%. Comparing base (82fa82e) to head (ffa82f8).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1368      +/-   ##
==========================================
+ Coverage   84.89%   84.90%   +0.01%     
==========================================
  Files         113      113              
  Lines       28923    28923              
  Branches    28923    28923              
==========================================
+ Hits        24553    24556       +3     
+ Misses       3198     3197       -1     
+ Partials     1172     1170       -2     

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[zachschuermann]

LGTM