[WIP] attach metadata to each individual message in bulkpublish if it exists

[cwalsh2189]

Description

Currently the bulk publish metadata is only applied to the BulkPublishRequest object and not the individual messages within. Attaching the metadata to the individual messages as well so they can be applied when those are read.

Issue reference

We strive to have all PR being opened based on an issue, where the problem or feature have been discussed prior to implementation.

Please reference the issue this PR will close: #1421

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• [] Extended the documentation

[cwalsh2189]

I was not sure what the full expectation for this change would be so wanted some feedback. It appears that this is impacting all consumers and not just Azure/Service Bus as in the open issue. We utilize AWS SNS/SQS and are seeing the same thing.

I went the route of applying the metadata to each individual message and leaving it at the top level, but not sure if that is still necessary/required, or if that piece should be removed.