Apply recursion limit without std

[LucaCappelletti94]

Parser::with_recursion_limit documented a hard parser depth limit, but builds without std used a stub RecursionCounter that always succeeded. Deeply nested input could overflow the stack instead of returning ParserError::RecursionLimitExceeded.

This makes the counter use alloc::rc::Rc and core::cell::Cell, which are available without std, and adds a --no default-features runtime test to the no-std CI path.