New lint: needless_owned_generic_args

[Tunglies]

Adds a new restriction lint needless_owned_generic_args that detects owned,
non-Copy values passed by value to a function-level generic type parameter
when a shared reference to the value would also satisfy the callee's complete
instantiated predicate set:

fn read(path: impl AsRef<Path>) {}

let path = PathBuf::from("/tmp");
read(path);

Use instead:

read(&path);

Explicit Clone::clone calls in such argument positions are detected too
(read(path.clone()) -> read(&path)).

How it works

The lint builds &A, substitutes it for exactly the one function-level generic
argument in the callee's GenericArgs, re-instantiates all caller bounds of
the callee, and proves each with predicate_must_hold_modulo_regions (same
idiom as useless_conversion / needless_borrows_for_generic_args). It is
deliberately conservative and skips:

• formal parameters that are not directly a type parameter (e.g. Option<T>)
• impl/trait-level or Self parameters
• parameters occurring more than once in the signature (shared by another
  argument, or appearing in the return type)
• calls with explicit turbofish
• Copy values, references, temporaries, and non-place expressions
• types marked #[clippy::has_significant_drop] (e.g. MutexGuard)
• .clone() calls that do not resolve to Clone::clone

It is the ownership-policy counterpart of needless_borrows_for_generic_args
(&T -> T, see #12454 / #12706): that lint only removes borrows of Copy
values, temporaries, and uniquely-used mutable references, so the two lints
cannot produce a fix-loop (covered by a .fixed UI test that recompiles
warning-free with both lint groups active). The duplicated path_has_args
helper was replaced by clippy_utils::last_path_segment.

Since impl Trait for T and impl Trait for &T may behave differently and
moving changes drop location, the lint is in the restriction group and the
suggestion is MaybeIncorrect.

Performance: candidate arguments are filtered with cheap HIR checks before any
signature/predicate queries run. Measured overhead of the lint pass is below
wall-clock noise on clippy_lints itself; the trait-solver cost is roughly
25us per emitted lint (2000 hits in ~47ms).

changelog: new lint: [needless_owned_generic_args]

LLM usage disclosure

This PR (implementation, tests, and this description) was drafted with LLM
assistance. The changes were built and verified locally before submission:
cargo test (including the new UI tests and dogfood), cargo dev fmt, and
cargo dev update_lints --check all pass.

• Followed lint naming conventions
• Added passing UI tests (including committed .stderr file)
• cargo test passes locally
• Executed cargo dev update_lints
• Added lint documentation
• Run cargo dev fmt

[rustbot]

Thanks for the pull request, and welcome!

You should hear from one of our reviewers after this PR gets at least 2 reviews from the community.

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[github-actions]

Lintcheck changes for b5217fc

Lint	Added	Removed	Changed
clippy::needless_owned_generic_args	688	0	0

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