Remove `sbrk` and `LeakingAllocator` from `polkavm_derive` 

polkavm-derive: use `#[unsafe(no_mangle)]` for `__atomic_fetch_add_8`… … polyfill

Make `assemble` public (but hidden) 

Bump `polkavm` to 0.29.1 

Bump version to 0.29.0 

Bump version to 0.28.0 

Bump version to 0.27.0 

Silence clippy in `bench-prime-sieve` on the new Rust toolchain 

polkavm-linker: fix atomic instructions with zero operand 

Bump version to 0.24.0