Remove remaining GitHub crates from `nexus-sdk`

[aelesbao]

Description

Now that we removed the dependency on the sui-sdk from MystenLab's GitHub, we should cleanup the remaining GitHub crate references from nexus-sdk.

This way, we will be able to deploy nexus-cli, nexus-sdk, and nexus-toolkit to crates.io and provide a standardized source of truth for downstream clients.

[kouks]

We still technically depend on sui-sdk from MystenLabs/sui but that's only for compiling and building move modules - these dependencies are only used in tests.

The problem is that these test dependencies are reused in the leader for e2e testing so they cannot just be marked as dev-dependencies. At the moment they are locked behind the test_utils feature.

We basically have 2 options here:

• find another way to compile and build move packages that doesn't depend on sui-sdk
• remove the test_utils feature from the SDK (and mark the dependencies as dev) and duplicate the move build code in the leader

[kouks]

We still actually depend on our own fork of testcontainers-modules but that's the exact same argument.

[kouks]

Another idea is to extract this test_utils feature out of nexus-sdk into a separate crate nexus-test-utils - then both the SDK and the leader can "dev-depend" on this github-hosted crate - this is IMO the simplest and maybe event cleanest solution.