docs: fix malformed rustdoc for bit_and/bit_or/bit_xor expr fns

[jackylee-ch]

Which issue does this PR close?

• N/A

Rationale for this change

The bit_and/bit_or/bit_xor expr helpers build their rustdoc in the make_bitwise_udaf_expr_and_func! macro by concat!-ing "Returns the bitwise", stringify!($OPR_TYPE) and "of a group of values" with no separators. Since stringify!(BitwiseOperationType::And) is BitwiseOperationType :: And, docs.rs renders Returns the bitwiseBitwiseOperationType :: Andof a group of values.

What changes are included in this PR?

The macro now takes a readable operation name ("AND"/"OR"/"XOR"), producing Returns the bitwise AND of a group of values.

What is the testing strategy for this PR?

cargo doc -p datafusion-functions-aggregate: the three expr fns now render Returns the bitwise {AND,OR,XOR} of a group of values.

Are there any user-facing changes?

Corrected rustdoc for the bit_and/bit_or/bit_xor expression functions. No behavior change.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.64%. Comparing base (7c67e4c) to head (bc13904).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #25997      +/-   ##
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- Coverage   82.64%   82.64%   -0.01%     
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  Files        1147     1147              
  Lines      445491   445502      +11     
  Branches   445491   445502      +11     
==========================================
+ Hits       368162   368164       +2     
- Misses      54972    54979       +7     
- Partials    22357    22359       +2     

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