Replace ast::TokenKind::BinOp{,Eq} and remove BinOpToken.

`BinOpToken` is badly named, because it only covers the assignable
binary ops and excludes comparisons and `&&`/`||`. Its use in
`ast::TokenKind` does allow a small amount of code sharing, but it's a
clumsy factoring.

This commit removes `ast::TokenKind::BinOp{,Eq}`, replacing each one
with 10 individual variants. This makes `ast::TokenKind` more similar to
`rustc_lexer::TokenKind`, which has individual variants for all
operators.

Although the number of lines of code increases, the number of chars
decreases due to the frequent use of shorter names like `token::Plus`
instead of `token::BinOp(BinOpToken::Plus)`.

compiler/rustc_parse/src/parser/path.rs

@@ -305,10 +305,7 @@ impl<'a> Parser<'a> {
         let is_args_start = |token: &Token| {
             matches!(
                 token.kind,
-                token::Lt
-                    | token::BinOp(token::Shl)
-                    | token::OpenDelim(Delimiter::Parenthesis)
-                    | token::LArrow
+                token::Lt | token::Shl | token::OpenDelim(Delimiter::Parenthesis) | token::LArrow
             )
         };
         let check_args_start = |this: &mut Self| {