clippy: fix several lint warns (#32126)

As seems #31500 still remain opened here's the next partial fix.

Fixed list: `unused_mut`, `clippy::needless_borrow`,
`clippy::match_ref_pats`, `clippy::borrow_deref_ref`, `clippy::ptr_eq`,
`clippy::unnecessary_cast`, `clippy::derivable_impls`,
`clippy::collapsible_match`, `clippy::extra_unused_lifetimes`,
`clippy::map_clone`, `clippy::manual_filter`.


- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes are part of #31500.
- [x] These changes do not require tests because are only cosmetic.

components/script/dom/htmlformelement.rs

@@ -1569,10 +1569,9 @@ pub trait FormControl: DomObject {
                 if html_elem.is_form_associated_custom_element() {
                     ScriptThread::enqueue_callback_reaction(
                         elem,
-                        CallbackReaction::FormAssociated(match new_owner {
-                            None => None,
-                            Some(ref form) => Some(DomRoot::from_ref(&**form)),
-                        }),
+                        CallbackReaction::FormAssociated(
+                            new_owner.as_ref().map(|form| DomRoot::from_ref(&**form)),
+                        ),
                         None,
                     )
                 }