docs: Point SessionConfig setter/getter docs to the config definitions

[2010YOUY01]

Which issue does this PR close?

• Closes Clean-up config setter/getter doc comments #25101.

Rationale for this change

A configuration option's main documentation lives on the config field definition in datafusion_common::config, since the user guide (https://datafusion.apache.org/user-guide/configs.html) is generated from there. Some SessionConfig setters/getters re-explained the option in their own words, which drifts from the definition over time (and in some cases already had). Keeping the wrapper docs as a plain link to the definition keeps the documentation centralized.

What changes are included in this PR?

Every SessionConfig setter/getter that wraps a single config field now uses the same pattern already used by with_target_partitions / target_partitions:

/// Set [`repartition_joins`]
///
/// [`repartition_joins`]: datafusion_common::config::OptimizerOptions::repartition_joins

What is the testing strategy for this PR?

NA

Are there any user-facing changes?

NO

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.80%. Comparing base (bf01e28) to head (50aaca4).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #25102      +/-   ##
==========================================
- Coverage   81.80%   81.80%   -0.01%     
==========================================
  Files        1130     1130              
  Lines      417707   417708       +1     
  Branches   417707   417708       +1     
==========================================
- Hits       341708   341687      -21     
- Misses      55875    55890      +15     
- Partials    20124    20131       +7     

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