Today, when adding a new integration test with its own configuration requirements, we need to either:

1. Create/clone an Envoy config, with some amount of boilerplate, or
2. Reuse an existing config, adding in listeners/filters etc. unrelated to the original config.

Ideally, we would be able to programatically generate configs, with a common base and per-test customization. This might be much more feasible in v2 where we have proto objects to build the configs.