This removes workspace hack from all libs, not from any binaries. This
does not change the behaviour of the hack.
Running
```
cargo clean
cargo build --release --bin proxy
```
Before this change took 5m16s. After this change took 3m3s. This is
because this allows the build to be parallelisable much more.
Create Rust bindings for C functions from walproposer. This allows to
write better tests with real walproposer code without spawning multiple
processes and starting up the whole environment.
`make walproposer-lib` stage was added to build static libraries
`libwalproposer.a`, `libpgport.a`, `libpgcommon.a`. These libraries can
be statically linked to any executable to call walproposer functions.
`libs/walproposer/src/walproposer.rs` contains
`test_simple_sync_safekeepers` to test that walproposer can be called
from Rust to emulate sync_safekeepers logic. It can also be used as a
usage example.
