Rollup merge of #119231 - aDotInTheVoid:PatKind-struct-bool-docs, r=compiler-errors

Clairify `ast::PatKind::Struct` presese of `..` by using an enum instead of a bool

The bool is mainly used for when a `..` is present, but it is also set on recovery to avoid errors. The doc comment not describes both of these cases.

See cee794ee98/compiler/rustc_parse/src/parser/pat.rs (L890-L897) for the only place this is constructed.

r? ``@compiler-errors``

clippy_lints/src/unnested_or_patterns.rs

@@ -293,7 +293,7 @@ fn extend_with_struct_pat(
     qself1: &Option<P<ast::QSelf>>,
     path1: &ast::Path,
     fps1: &mut [ast::PatField],
-    rest1: bool,
+    rest1: ast::PatFieldsRest,
     start: usize,
     alternatives: &mut ThinVec<P<Pat>>,
 ) -> bool {