Enable more clippy lints

[emilk]

Which issue does this PR close?

• Part of Stricter Clippy checks in CI #18467.

Rationale for this change

Continuing #24466: turn on more clippy::pedantic lints (opt-out list in Cargo.toml).

What changes are included in this PR?

One commit per lint, each removing its "allow" line from Cargo.toml
and fixing every site. Review one commit at a time!

Let me know if you disagree with any and I'll revert it

Lint	Sites	Fix
no_effect_underscore_binding	1	removed a dead let _expected = … binding
case_sensitive_file_extension_comparisons	1	Path::extension() instead of str::ends_with(".csv")
cast_ptr_alignment	5	#[expect] on FFI tests that downcast to a concrete, aligned type
doc_link_with_quotes	25	quoted doc "links" turned into real intra-doc links or backticked code
ref_option	36	&Option<T> params/returns changed to Option<&T>
needless_continue	37	dropped continues that already ended the loop iteration
cloned_instead_of_copied	38	copied() instead of cloned() for Copy types
unnecessary_semicolon	185	dropped semicolons after tail match/if
unnecessary_trailing_comma	49	dropped trailing commas after single-item parens/brackets

The ref_option commit also changes the signature of the public apply_masking fn in datafusion-substrait (&Option<MaskExpression> -> Option<&MaskExpression>), since it forwards to an internal fn that was flagged.

Are these changes tested?

cargo clippy --workspace --all-targets --all-features reports no
warnings. The changes are mechanical and behavior-preserving, so no new
tests.

Are there any user-facing changes?

The ref_option commit changes the public apply_masking signature in
datafusion-substrait, see above.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 84.55744% with 82 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.37%. Comparing base (5f0ba13) to head (3965bd2).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...tafusion/functions-aggregate-common/src/min_max.rs	91.37%	10 Missing ⚠️
datafusion/common/src/format.rs	27.27%	0 Missing and 8 partials ⚠️
datafusion/functions/src/regex/mod.rs	30.00%	7 Missing ⚠️
...gate-common/src/aggregate/count_distinct/native.rs	14.28%	6 Missing ⚠️
datafusion/functions/src/datetime/date_trunc.rs	88.88%	5 Missing and 1 partial ⚠️
...tafusion/common/src/file_options/parquet_writer.rs	37.50%	0 Missing and 5 partials ⚠️
datafusion/expr/src/logical_plan/display.rs	0.00%	4 Missing ⚠️
datafusion/sql/src/parser.rs	73.33%	1 Missing and 3 partials ⚠️
...egate-common/src/aggregate/count_distinct/bytes.rs	0.00%	0 Missing and 2 partials ⚠️
datafusion/physical-plan/src/test/exec.rs	0.00%	2 Missing ⚠️
... and 26 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #24566      +/-   ##
==========================================
+ Coverage   81.34%   81.37%   +0.02%     
==========================================
  Files        1117     1117              
  Lines      397528   398005     +477     
  Branches   397528   398005     +477     
==========================================
+ Hits       323385   323857     +472     
- Misses      55225    55227       +2     
- Partials    18918    18921       +3     

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