Description
#### Problem
Missing a test that verifies the `AccountInfo`'s data length is correctly enforced to exist in RW data. The length is translated correctly but we have no way to ensure that it will continue to do so over time.
https://github.com/solana-labs/solana/blob/5dceddd21d3c1cf874b003a0c25b1f21f4926614/programs/bpf/rust/ro_modify/src/lib.rs#L158
#### Proposed Solution
`AccountInfo`'s data is expressed as an `Rc<RefCell<&mut [u8]>>`, need a way to construct this where the slice's len is in RO memory (like the RO segment of a BPF ELF) while the data pointer points to RW memory. This is not a use case that can be activated without malicious intent.