chore: add script to validate changes to network_config.json

[alexghr]

This PR adds a script (100% claude) that pulls the diff from a PR against https://github.com/AztecProtocol/networks, spawns two nodes and waits to see if (1) the nodes can snapshot sync and (2) they find each other (ie the new bootnodes work).

How to run:

1. setup gcloud, kubectl
2. Run ./spartan/scripts/pr_network_validate.sh 10 mainnet to test AztecProtocol/networks#10
3. wait
4. script says yay/nay

[AztecBot]

Flakey Tests

🤖 says: This CI run detected 2 tests that failed, but were tolerated due to a .test_patterns.yml entry.

\033[38;2;188;109;208mFLAKED\033[0m (\033[38;2;250;217;121m8;;http://ci.aztec-labs.com/6e1e69add0b49a376e1e69add0b49a378;;\033[0m): yarn-project/end-to-end/scripts/run_test.sh simple src/e2e_p2p/multiple_validators_sentinel.parallel.test.ts "collects attestations for validators in proposer node when block is not published" (135s) (code: 1) group:e2e-p2p-epoch-flakes (\033[38;2;188;109;208mAlex Gherghisan\033[0m: chore: update script)
\033[38;2;188;109;208mFLAKED\033[0m (\033[38;2;250;217;121m8;;http://ci.aztec-labs.com/5f919d511db636565f919d511db636568;;\033[0m): yarn-project/end-to-end/scripts/run_test.sh simple src/e2e_epochs/epochs_multi_proof.test.ts (170s) (code: 1) group:e2e-p2p-epoch-flakes (\033[38;2;188;109;208mAlex Gherghisan\033[0m: chore: update script)