* Fix C headers (the name of the syscall was incorrect).
* Add C SBF tests using the alt_bn128 syscall.
* Fix the Rust SBF program:
* Do not use serde and array-bytes, provide test cases as byte arrays
directly.
* Use the `custom_heap_default` macro.
* Replace `bpf` with `sbf` in the crate name.
* Execute both previously existing Rust tests and new C tests in
`programs/sbf/tests`, so they are actually tested on CI.