syntax: Parses && as & & whenever appropriate.

[lifthrasiir]

Uses the same strategy as || and >>. Closes #11227.

[huonw]

❤️

(If you're feeling like being doubly-awesome, #13324 is similar.)

[lifthrasiir]

@huonw Huh, that actually make me rethink about the entire strategy currently used with || and >>. Technically we can replace Parser::bump with Parser::expect plus a partial token handling, but we already have a heap of matches that cannot be easily refactored without replacing them with multiple conditionals which prevents the refactoring. Well, I'd leave this commit as is for now.

[brson]

How amenable is this strategy of "undoing" what the lexer has already done to being adapted to a more "normal" grammar? I.e. it seems like this is a huge flaw in the lexer that this fixup is required.