Add chaos testing framework for ldk-server

Introduce ldk-server-chaos, a testing harness that stress-tests ldk-server
by running multiple nodes, opening channels, and continuously sending
payments while randomly killing and restarting nodes.

Features:
- Spawns 3 ldk-server nodes with auto-generated configs
- Creates a fully connected channel topology
- Runs concurrent payment loops between all node pairs
- Randomly kills and restarts nodes to test resilience
- Tracks payment success rates and detects timeout failures
- Uses bitcoind RPC for on-chain operations and block generation

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: joostjager

.gitignore

@@ -1 +1,2 @@
 /target
+/ldk-server-chaos/data