wrap else to next line if let-else pattern is multi-lined

This rule wasn't explicity stated in the style guide so it was missed,
but luckily we caught it during testing.

src/items.rs

@@ -127,8 +127,8 @@ impl Rewrite for ast::Local {
 
             if let Some(block) = else_block {
                 let else_kw_span = init.span.between(block.span);
-                let force_newline_else =
-                    !same_line_else_kw_and_brace(&result, context, else_kw_span, nested_shape);
+                let force_newline_else = pat_str.contains('\n')
+                    || !same_line_else_kw_and_brace(&result, context, else_kw_span, nested_shape);
                 let else_kw = rewrite_else_kw_with_comments(
                     force_newline_else,
                     true,

tests/target/configs/single_line_let_else_max_width/100.rs

@@ -24,7 +24,8 @@ fn main() {
         upper,
         step,
         range: _,
-    }) = slice.as_ref() else {
+    }) = slice.as_ref()
+    else {
         return;
     };
 

tests/target/configs/single_line_let_else_max_width/50.rs

@@ -26,7 +26,8 @@ fn main() {
         upper,
         step,
         range: _,
-    }) = slice.as_ref() else {
+    }) = slice.as_ref()
+    else {
         return;
     };
 

tests/target/configs/single_line_let_else_max_width/zero.rs

@@ -30,7 +30,8 @@ fn main() {
         upper,
         step,
         range: _,
-    }) = slice.as_ref() else {
+    }) = slice.as_ref()
+    else {
         return;
     };