fix: Quadratic allocations when loading nested Parquet column metadata

[coastalwhite]

Fixes #21031.

[codecov]

Codecov Report

Attention: Patch coverage is 61.90476% with 8 lines in your changes missing coverage. Please review.

Project coverage is 79.20%. Comparing base (2df0404) to head (e8a0d8e).
Report is 19 commits behind head on main.

Files with missing lines	Patch %	Lines
...-parquet/src/parquet/metadata/column_descriptor.rs	42.85%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #21050      +/-   ##
==========================================
+ Coverage   79.11%   79.20%   +0.09%     
==========================================
  Files        1583     1585       +2     
  Lines      225222   225583     +361     
  Branches     2586     2588       +2     
==========================================
+ Hits       178180   178684     +504     
+ Misses      46452    46309     -143     
  Partials      590      590              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.