Implement rename me -> self (#2444)

Implements change proposed in #1382

Replaces #1624

explorer/testdata/alias/class_alias.carbon

@@ -13,16 +13,16 @@
 package ExplorerTest api;
 
 interface Addable {
-  fn Add[me: Self](k: i32) -> Self;
+  fn Add[self: Self](k: i32) -> Self;
 }
 impl i32 as Addable {
-  fn Add[me: Self](k: i32) -> Self { return me + k; }
+  fn Add[self: Self](k: i32) -> Self { return self + k; }
 }
 
 class Class { var n: i32; }
 class GenericClass(T:! Addable) {
   var m: T;
-  fn Get[me: Self](n: i32) -> T { return me.m.Add(n); }
+  fn Get[self: Self](n: i32) -> T { return self.m.Add(n); }
 }
 
 alias ClassAlias = Class;

explorer/testdata/alias/member_name_alias.carbon

@@ -11,19 +11,19 @@ package ExplorerTest api;
 
 interface I {
   fn F() -> i32;
-  fn M[me: Self]() -> i32;
+  fn M[self: Self]() -> i32;
 }
 class A {
   var n: i32;
   impl as I {
     fn F() -> i32 { return 1; }
-    fn M[me: Self]() -> i32 { return 2; }
+    fn M[self: Self]() -> i32 { return 2; }
   }
-  fn G[me: Self]() -> i32 { return 3; }
+  fn G[self: Self]() -> i32 { return 3; }
 }
 impl i32 as I {
   fn F() -> i32 { return 4; }
-  fn M[me: Self]() -> i32 { return 5; }
+  fn M[self: Self]() -> i32 { return 5; }
 }
 
 alias IF = I.F;