Don't recover lifetimes/labels containing emojis as character literals

Note that at the time of this commit, `unic-emoji-char` seems to have
data tables only up to Unicode 5.0, but Unicode is already newer than
this.

A newer emoji such as `🥺` will not be recognized as an emoji
but older emojis such as `🐱` will.

compiler/rustc_errors/src/lib.rs

@@ -471,6 +471,8 @@ pub enum StashKey {
     /// When an invalid lifetime e.g. `'2` should be reinterpreted
     /// as a char literal in the parser
     LifetimeIsChar,
+    /// When an invalid lifetime e.g. `'🐱` contains emoji.
+    LifetimeContainsEmoji,
     /// Maybe there was a typo where a comma was forgotten before
     /// FRU syntax
     MaybeFruTypo,