Add ethrex EL client to bal-devnet-2

[qu0b]

Summary

• Add ethrex (lambdaclass/ethrex) Rust EL client to terraform hetzner node definitions and ansible config
• Adds lighthouse+ethrex and lodestar+ethrex combos for both super and full node types
• All node counts set to 0 (disabled) — ready to enable once the ansible role lands

Changes

• terraform/devnet-2/hetzner/nodes.tf: 4 new variable blocks (lighthouse/lodestar x super/full)
• terraform/devnet-2/hetzner/main.tf: Added ethrex entries to vm_groups list
• terraform/devnet-2/ansible_inventory.tmpl: Added ethrex to EL clients list for inventory group generation
• ansible/inventories/devnet-2/group_vars/all/images.yaml: Added ethrex: ethpandaops/ethrex:bal-devnet-2
• ansible/inventories/devnet-2/group_vars/ethrex.yaml: New file with ethrex container config, SSH keys for top lambdaclass contributors, prometheus scrape config

Dependencies

• Requires ethpandaops/ansible-collection-general ethrex role (previous attempt: PR #498 was closed)
• Nodes are disabled (count=0) until the ansible role is available

Testing

• Ethrex bal-devnet-2 branch tested locally in Kurtosis with lodestar CL + full spamoor load (evm-fuzz 220tps, eoatx 30tps, uniswap-swaps 30tps)
• 158 slots, 0 errors, chain finalizing, 100% gas blocks under load
• Fulu-era validated; Gloas-era blocked by lodestar minimal preset bug (not an ethrex issue)

Test plan

• Verify terraform plan succeeds with no resource changes (count=0)
• Once ansible role lands upstream, set count=1 and deploy

🤖 Generated with Claude Code

[edg-l]

I reopened ethpandaops/ansible-collection-general#498, at that time i wasnt sure if we wanted to add ethrex, but now we have most hive tests passing