Adapt to new polkadot binaries split

[BulatSaif]

Fixes #40

Changes:

1. Fixed a typo in the key inject role.
2. Adapted to the new binary split for validators.
3. Added migration checks: After downloading the new binary, the help command is used to verify the presence of necessary flags. We check --help output instead of the --version since the role may deploy any Substrate chain, and the version format can vary.

Tests

I used a binary from the master branch (link may have expired): Binary Link

Case 1:
Using the old ansible role results in a failure:

2023-08-08 16:37:33.992  WARN tokio-runtime-worker sc_service::builder: The NetworkStart returned as part of `build_network` has been silently dropped
Error:
   0: Worker binaries could not be found. Ensure that polkadot was built/installed correctly. Searched given workers path (None), polkadot binary path ("/home/parity/bin"), and lib path (/usr/lib/polkadot), worker names: None

Case 2:
Using the new ansible role from this branch results in successful application execution:

2023-08-08 16:31:26.134  INFO main polkadot_service: 🚀 Using the prepare-worker binary at: "/home/parity/bin/polkadot-prepare-worker"
2023-08-08 16:31:26.134  INFO main polkadot_service: 🚀 Using the execute-worker binary at: "/home/parity/bin/polkadot-execute-worker"