not setting queue_url bucket_arn or non_aws_bucket_name returns error

[francescayeye]

Breaking Change

What does this PR do?

In case an aws-s3 input has no source param defined in the config (either queue_url, bucket_arn or non_aws_bucket_name) loading the input will return an error on config validation and stop Filebeat

Why is it important?

Giving a proper blocking failure error message instead of silently fail loading the input will improve troubleshooting issue in the aws s3 input.
The same solution was not possible in 7.x due to loading and validating every filesets existing for a module regardless they were configured or not

Checklist

• My code follows the style guidelines of this project
  - [ ] I have commented my code, particularly in hard-to-understand areas
  - [ ] I have made corresponding changes to the documentation
  - [ ] I have made corresponding change to the default configuration files
  - [ ] I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Author's Checklist

• [ ]

How to test this PR locally

Related issues

Relates #13911
Requires #27526

Use cases

Screenshots

Logs

2021-10-27T10:56:40.896+0200    INFO    instance/beat.go:495    filebeat stopped.
2021-10-27T10:56:40.896+0200    ERROR   instance/beat.go:992    Exiting: Failed to start crawler: starting input failed: Error while initializing input: neither queue_url, bucket_arn nor non_aws_bucket_name were provided, input aws-s3 will stop accessing config

[mergify]

This pull request does not have a backport label. Could you fix it @aspacca? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v./d./d./d is the label to automatically backport to the 7./d branch. /d is the digit

NOTE: backport-skip has been added to this pull request.

[elasticmachine]

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