`validate` command does not validate pipeline type

[andrzej-stencel]

Describe the bug

Thew validate command intoduced in #7835 does not validate the type of pipeline a component is assigned to. For example, if a metrics-only component is used in a logs pipeline, validation passes, but I would expect it to fail.

Steps to reproduce

• Download the latest contrib distro (to have access to various types of components) from https://github.com/open-telemetry/opentelemetry-collector-releases/releases/tag/v0.80.0
• Prepare a config file that uses components in invalid pipeline types, see below.
• Run the collector to verify that the configuration is invalid:

$ otelcol-contrib-0.80.0-linux_amd64 --config config.yaml 
2023-07-03T11:49:33.120+0200    info    service/telemetry.go:81 Setting up own telemetry...
2023-07-03T11:49:33.120+0200    info    service/telemetry.go:104        Serving Prometheus metrics      {"address": ":8888", "level": "Basic"}
2023-07-03T11:49:33.120+0200    info    exporter@v0.80.0/exporter.go:275        Stability level of component is undefined       {"kind": "exporter", "data_type": "logs", "name": "prometheus"}
Error: failed to build pipelines: failed to create "prometheus" exporter for data type "logs": telemetry type is not supported
2023/07/03 11:49:33 collector server run finished with error: failed to build pipelines: failed to create "prometheus" exporter for data type "logs": telemetry type is not supported

• Run the validate command:

$ otelcol-contrib-0.80.0-linux_amd64 validate --config config.yaml
$ echo $?
0

What did you expect to see?
Validation fails

What did you see instead?
Validation succeeds

What version did you use?
v0.80.0

What config did you use?

exporters:
  awscloudwatchlogs:
    log_group_name: x
    log_stream_name: x
  jaeger:
    endpoint: x
  prometheus:

receivers:
  filelog:
  httpcheck:
    endpoint: x
  zipkin:

service:
  pipelines:
    logs:
      exporters:
      - prometheus # metrics-only
      receivers:
      - zipkin # traces-only

    metrics:
      exporters:
      - jaeger # traces-only
      receivers:
      - filelog # logs-only

    traces:
      exporters:
      - awscloudwatchlogs # logs-only
      receivers:
      - httpcheck # metrics-only

Environment
OS: Ubuntu 23.04 lunar

Additional context

Currently, there is no documentation describing to what extent the validation works. I believe it's reasonable for the user to assume the pipeline types would be validated. I understand that what the validate command does under the hood is just run Validate() on the config object.

[ycombinator]

I would like to work on this one.

[andrzej-stencel]

Sounds great @ycombinator, assigning the issue to you.