Rollup merge of #123752 - estebank:emoji-prefix, r=wesleywiser

Properly handle emojis as literal prefix in macros

Do not accept the following

```rust
macro_rules! lexes {($($_:tt)*) => {}}
lexes!(🐛"foo");
```

Before, invalid emoji identifiers were gated during parsing instead of lexing in all cases, but this didn't account for macro pre-expansion of literal prefixes.

Fix #123696.

Author: workingjubilee