Auto merge of #16372 - davidsemakula:import-granularity-one, r=Veykril

feat: Add "One" import granularity

Adds a new import granularity option "One" that merges all imports into a single use statement as long as they have the same visibility and attributes.

This is similar to [rustfmt's `imports_granularity = "One"`](https://rust-lang.github.io/rustfmt/?version=v1.6.0&search=import#imports_granularity).

Fixes: #11361

crates/syntax/src/ast/edit_in_place.rs

@@ -1,6 +1,6 @@
 //! Structural editing for ast.
 
-use std::iter::{empty, successors};
+use std::iter::{empty, once, successors};
 
 use parser::{SyntaxKind, T};
 
@@ -530,6 +530,25 @@ impl ast::UseTree {
             Some(())
         }
     }
+
+    /// Wraps the use tree in use tree list with no top level path (if it isn't already).
+    ///
+    /// # Examples
+    ///
+    /// `foo::bar` -> `{foo::bar}`
+    ///
+    /// `{foo::bar}` -> `{foo::bar}`
+    pub fn wrap_in_tree_list(&self) {
+        if self.path().is_none() {
+            return;
+        }
+        let subtree = self.clone_subtree().clone_for_update();
+        ted::remove_all_iter(self.syntax().children_with_tokens());
+        ted::append_child(
+            self.syntax(),
+            make::use_tree_list(once(subtree)).clone_for_update().syntax(),
+        );
+    }
 }
 
 impl ast::UseTreeList {

crates/syntax/src/ast/node_ext.rs

@@ -327,6 +327,14 @@ impl ast::UseTree {
     pub fn parent_use_tree_list(&self) -> Option<ast::UseTreeList> {
         self.syntax().parent().and_then(ast::UseTreeList::cast)
     }
+
+    pub fn top_use_tree(&self) -> ast::UseTree {
+        let mut this = self.clone();
+        while let Some(use_tree_list) = this.parent_use_tree_list() {
+            this = use_tree_list.parent_use_tree();
+        }
+        this
+    }
 }
 
 impl ast::UseTreeList {