[DOP-21732] Fix Oracle reading with partitioning_mode=hash

[dolfinus]

Change Summary

ORA_HASH(col, N) returns results from 0 to N including N (N+1 in total). Spark creates exactly N partitions, so last partition gets twice the data relative to other ones.

Fixed by calling ORA_HASH(col, N-1). Other JDBC sources don't have such an issue, as they use modulo which always returns values from 0 to N-1.

Related issue number

Checklist

• Commit message and PR title is comprehensive
• Keep the change as small as possible
• Unit and integration tests for the changes exist
• Tests pass on CI and coverage does not decrease
• Documentation reflects the changes where applicable
• docs/changelog/next_release/<pull request or issue id>.<change type>.rst file added describing change
  (see CONTRIBUTING.rst for details.)
• My PR is ready to review.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.84%. Comparing base (8c39d1d) to head (e974d34).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #319      +/-   ##
===========================================
+ Coverage    91.67%   91.84%   +0.16%     
===========================================
  Files          225      225              
  Lines         9649     9649              
  Branches       987      987              
===========================================
+ Hits          8846     8862      +16     
+ Misses         608      593      -15     
+ Partials       195      194       -1     

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