Change zombienet binary

[RafalMirowski1]

#28

Changed zombienet binary, encountered issue where relative paths in zombienet.toml were not working so also intorduced PROJECT_ROOT env variable which is used in zombienet.toml like default_command = "{{PROJECT_ROOT}}/.bin/polkadot"

[RafalMirowski1]

It looks like new zombie-cli binary is not straight-forwardly compatible with being run inside paritytech/ci-unified:bullseye. It fails with missing libssl3: https://github.com/paritytech/web3-storage/actions/runs/22950511272/job/66613712436 and even when we add libssl3, libc is incompatible: https://github.com/paritytech/web3-storage/actions/runs/22950984655/job/66615310176. Running on ubuntu-latest works, but not sure we wanna do this.
Maybe we should ask for a compatible binary to be built? @bkontur @karolk91 wdyt?

[karolk91]

@RafalMirowski1, I think you could separate the process of building whatever is necessary (this would use the ci-unified image), and once you have all the binaries built (or maybe downloaded from cache) you could then have a separate step (which uses ubuntu image) to run the zombienet network and tests

I guess the questions are:

• why do we need to use ci-unified image? - IMHO, if we need to build any rust project, its good to re-use the image that polkadot-sdk uses for runtime builds reproducibility etc
• do we need to use ci-unified image for non-rust related stuff? - I think we dont need to
• can we run ubuntu images on parity runners? - I think we can find examples of this in the wild so I guess its not an issue