[extension/observer/docker, receiver/dockerstats] Add hint about api_version

[mx-psi]

Description:

Adds a hint like this to api_version:

Hint: You may want to wrap the 'api_version' value in quotes (api_version: "1.25")

Testing:

docker_stats config and output

Config

receivers:
  docker_stats:
    collection_interval: 2s
    api_version: 1.25 # Floating value

exporters:
  nop:

service:
  pipelines:
    metrics:
      receivers: [docker_stats]
      exporters: [nop]

Output

Error: failed to get config: cannot unmarshal the configuration: 1 error(s) decoding:

* error decoding 'receivers': error reading configuration for "docker_stats": 1 error(s) decoding:

* 'api_version' expected type 'string', got unconvertible type 'float64', value: '1.25'.

Hint: You may want to wrap the 'api_version' value in quotes (api_version: "1.25")

Hint: Temporarily restore the previous behavior by disabling 
      the `confmap.strictlyTypedInput` feature gate. More details at:
      https://github.com/open-telemetry/opentelemetry-collector/issues/10552

docker_observer config and output

receivers:
  nop:

exporters:
  nop:

extensions:
  docker_observer:
    api_version: 1.25

service:
  extensions: [docker_observer]
  pipelines:
    metrics:
      receivers: [nop]
      exporters: [nop]

Error: failed to get config: cannot unmarshal the configuration: 1 error(s) decoding:

* error decoding 'extensions': error reading configuration for "docker_observer": 1 error(s) decoding:

* 'api_version' expected type 'string', got unconvertible type 'float64', value: '1.25'.

Hint: You may want to wrap the 'api_version' value in quotes (api_version: "1.25")

Hint: Temporarily restore the previous behavior by disabling 
      the `confmap.strictlyTypedInput` feature gate. More details at:
      https://github.com/open-telemetry/opentelemetry-collector/issues/10552

[atoulme]

The changes look ok, but wouldn't you like to add a unit test for them as well?

[mx-psi]

The changes look ok, but wouldn't you like to add a unit test for them as well?

Yes, but to do that easily I have to merge #34055 first