ecs_task_observer: initial structure

[rmfitzpatrick]

Description:
Adding a feature - These changes introduce a new receiver creator-compatible watch observer for ECS tasks. It differs from the existing ECS observer in that it supports only sidecar deployments and doesn't have a hard dependency on the Prometheus receiver, instead being able to sync with a receiver creator instance by listing container endpoints. This approach was landed on after reviewing the existing and ECS observer config and implementation and from following the guidance of the initial observer's author: #5316 (comment). It does not resolve the outstanding item for #1395, as I think observer endpoint creation should be added to the existing observer as well but should be done in unrelated changes.

Link to tracking Issue:
#5316

Testing:
No tests as this time since the changes just include the initial types and readme. Basic factory test to help ensure receiver creator type compatibility.*

Documentation:
Adding a readme with high level plan and config documentation generated by project configschema tool.

cc @alolita

[bogdandrutu]

@Aneurysm9 would be good someone from AWS to review/own(coown) this

[Aneurysm9]

This looks like a nice addition. @rakyll I know you've talked about ways to improve ECS task detection, does this align with the direction you'd expect?

[Aneurysm9]

Using versioning file /home/runner/work/opentelemetry-collector-contrib/opentelemetry-collector-contrib/versions.yaml
verifyAllModulesInSet failed: Module github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/ecstaskobserver (defined in /home/runner/work/opentelemetry-collector-contrib/opentelemetry-collector-contrib/extension/observer/ecstaskobserver/go.mod) is not listed in any module set.

Please add this new module to versions.yaml.

[MovieStoreGuy]

I suggest using https://pkg.go.dev/github.com/stretchr/testify/assert#Implements to check if it implements the interface.

However, this feels like a redundant tests considering there is a compile time check

[rmfitzpatrick]

This test is for the factory method which wouldn't enforce the returned helper type at compile time, though the extension itself does have an added implementation check that could make this redundant. Given the level of indirection I think it's a helpful assurance.

Updated to use the implementation helper.

[rmfitzpatrick]

I believe this is ready to land, and the tests failures have been unrelated.

[tigrannajaryan]

@rmfitzpatrick please populate the commit message in future PRs (the PR description is typically great to use the commit message). I copy/pates this time before merging.