[receiver/sshcheck] Update test config and validate it in tests

[DewaldDeJager]

The test config file for the SSH check receiver is currently outdated - It uses keyfile in the config rather than key_file. This needs to be updated and the tests extended to pick up issues like this in future.

See the discussion in a related PR here #24676 (comment)_

[github-actions]

Pinging code owners:

• receiver/sshcheck: @nslaughter @codeboten

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[DewaldDeJager]

I'd be happy to work on this

[codeboten]

Thanks @DewaldDeJager!

[nslaughter]

I apologize. I've been absent from notifications, but I'm back. I see the issue. Thank you, @DewaldDeJager. Let me know if you would like assistance or I can handle.

[github-actions]

This issue has been inactive for 60 days. It will be closed in 60 days if there is no activity. To ping code owners by adding a component label, see Adding Labels via Comments, or if you are unsure of which component this issue relates to, please ping @open-telemetry/collector-contrib-triagers. If this issue is still relevant, please ping the code owners or leave a comment explaining why it is still relevant. Otherwise, please close it.

Pinging code owners:

• receiver/sshcheck: @nslaughter @codeboten

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[github-actions]

This issue has been closed as inactive because it has been stale for 120 days with no activity.