vmm: reevaluate #[allow] attributes

Remove stale #[allow]s whose lints no longer fire, convert the
unconditionally-firing ones to #[expect], and keep the
arch/feature-conditional ones as #[allow]. Verified across kvm/mshv,
x86_64/aarch64, and --all-features.

Part of #8326.

Signed-off-by: Tushar Khatri <hello@tusharkhatri.in>

vmm/src/api/http/mod.rs

@@ -98,7 +98,7 @@ const HTTP_ROOT: &str = "/api/v1";
 /// The error message contained in the response is supposed to be user-facing,
 /// thus insightful and helpful while balancing technical accuracy and
 /// simplicity.
-#[allow(clippy::needless_pass_by_value)]
+#[expect(clippy::needless_pass_by_value)]
 pub fn error_response(error: HttpError) -> Response {
     let mut response = Response::new(Version::Http11, error.status_code());
 

vmm/src/api/mod.rs

@@ -603,7 +603,7 @@ pub trait RequestHandler {
 pub type ApiRequest =
     Box<dyn FnOnce(&mut dyn RequestHandler) -> Result<bool, VmmError> + Send + 'static>;
 
-#[allow(clippy::needless_pass_by_value)]
+#[expect(clippy::needless_pass_by_value)]
 fn get_response<Action: ApiAction>(
     action: &Action,
     api_evt: EventFd,