Rollup merge of rust-lang#87267 - dtolnay:negspace, r=Aaron1011

Remove space after negative sign in Literal to_string

Negative proc macro literal tokens used to be printed with a space between the minus sign and the magnitude. That's because `impl ToString for Literal` used to convert the Literal into a TokenStream, which splits the minus sign into a separate Punct token.

```rust
Literal::isize_unsuffixed(-10).to_string()  // "- 10"
```

This PR updates the ToString impl to directly use `rustc_ast::token::Lit`'s ToString, which matches the way Rust negative numbers are idiomatically written without a space.

```rust
Literal::isize_unsuffixed(-10).to_string()  // "-10"
```

Author: JohnTitor

proc_macro/src/bridge/mod.rs

@@ -109,6 +109,7 @@ macro_rules! with_api {
                 fn drop($self: $S::Literal);
                 fn clone($self: &$S::Literal) -> $S::Literal;
                 fn from_str(s: &str) -> Result<$S::Literal, ()>;
+                fn to_string($self: &$S::Literal) -> String;
                 fn debug_kind($self: &$S::Literal) -> String;
                 fn symbol($self: &$S::Literal) -> String;
                 fn suffix($self: &$S::Literal) -> Option<String>;

proc_macro/src/lib.rs

@@ -1195,7 +1195,7 @@ impl FromStr for Literal {
 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 impl ToString for Literal {
     fn to_string(&self) -> String {
-        TokenStream::from(TokenTree::from(self.clone())).to_string()
+        self.0.to_string()
     }
 }