Fix Edge Cases in Password Callback Handling

Fix Edge Cases in Password Callback Handling

Fixes #8441: Modify the password callback handling to reserve one byte in the buffer for a null terminator, ensuring compatibility with legacy behavior that puts a terminating null byte at the end.

Additionally, validate the length returned by the callback to ensure it does not exceed the given buffer size. If the returned length is too large, the process now stops gracefully with an appropriate error, enhancing robustness by preventing crashes from out-of-bounds access.

Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/25330)