[rust-launcher] Add E2E flow test for launcher orchestration

[barakeinav1]

Context

Follow-up from PR #2326 (port node launcher to Rust). Tracked in #2598.

Problem

The Python launcher had test_main_nontee_builds_expected_mpc_docker_cmd which tested the full flow from config parsing through docker command assembly. The Rust launcher has no equivalent test for the run() function.

Action

Add an E2E test that mocks:

• Filesystem (config file, approved hashes file)
• Docker registry (token + manifest responses)
• Docker CLI commands (pull, inspect, compose)

And verifies the complete orchestration:

• Config is parsed correctly
• Image hash is selected
• Registry is queried
• Image is validated
• TEE config is injected
• Config file is written to shared volume
• Docker compose is rendered and launched

This likely requires extracting side-effectful operations behind traits or using a test harness.