[kong mesh] improve documentation for ecs controller

### Where is the problem?

https://docs.konghq.com/mesh/latest/installation/ecs/#kong-mesh-ecs-controller

### What happened?

There is basically no documentation regarding this controller. config options, ports, etc are all missing.

### What did you expect to happen?

I would expect to be able to find a reference to

- possible configurations and values
- default and expected ports
- more overall detail on what the controller does, how it functions, why its required, etc.

### Code of Conduct and Community Expectations

- [X] I agree to follow this project's Code of Conduct
- [X] I agree to abide by the Community Expectations

Start with the Kong Mesh ECS controller page at https://docs.konghq.com/mesh/latest/installation/ecs/#kong-mesh-ecs-controller and verify whether the work belongs in this archived repository or its successor. Identify the controller's configuration options, values, ports, purpose, and operation from the available project sources. Done means the page provides a complete reference covering each requested area.

Written by the indexing model from the issue text.