chore: enforce clippy::allow_attributes for datasource crates

[chakkk309]

Which issue does this PR close?

Part of #18881

Rationale for this change

Implement clippy::allow_attributes lint for datasource* crates

What changes are included in this PR?

1. Added lint enforcement: #![deny(clippy::allow_attributes)] to 6 datasource module mod.rs files
2. Attribute conversion: Changed 3 #[allow(...)] to #[expect(...)]:
   • deprecated
   • unused_imports
   • rustdoc::broken_intra_doc_links

Are these changes tested?

yes

Are there any user-facing changes?

No user-facing changes.

[alamb]

looks good to me -- thank you @chakkk309

[Jefffrey]

Thanks for picking this up, left some suggestions

[Jefffrey]

Could we also fix this instead of expecting it?

[chakkk309]

Hi, I've identified 2 options to address the #[expect(rustdoc::broken_intra_doc_links)] in datafusion-doc/src/lib.rs. Since datafusion-doc is designed as an independent crate without dependencies on other DataFusion crates, the original intra-doc links like ScalarUDFImpl cannot be resolved.

Option 1: Simple code references

 /// Documentation for use by `ScalarUDFImpl`, `AggregateUDFImpl` and `WindowUDFImpl` functions.`

Option 2: External links to docs.rs

  /// Documentation for use by [`ScalarUDFImpl`], [`AggregateUDFImpl`] and [`WindowUDFImpl`] functions.
  ///
  /// [`ScalarUDFImpl`]: https://docs.rs/datafusion-expr/latest/datafusion_expr/trait.ScalarUDFImpl.html
  /// [`AggregateUDFImpl`]: https://docs.rs/datafusion-expr/latest/datafusion_expr/trait.AggregateUDFImpl.html
  /// [`WindowUDFImpl`]: https://docs.rs/datafusion-expr/latest/datafusion_expr/trait.WindowUDFImpl.html

Which kind of method would we prefer for this use case?

[Jefffrey]

I think option 1 is sufficient

[Jefffrey]

Thanks @chakkk309 & @alamb