Add cache for `allocate_str` Best effort cache for string allocation in const eval. Fixes [rust-lang/miri#3470](https://github.com/rust-lang/miri/issues/3470).
Add cache for `allocate_str` Best effort cache for string allocation in const eval. Fixes [rust-lang/miri#3470](https://github.com/rust-lang/miri/issues/3470).