Remove batch publishing as its optimizations are now performed for "regular" publishes/outgoing frames

[bollhals]

Proposed Changes

Deletes the publish batch functionality. fixes part of #963

Types of Changes

• Bug fix (non-breaking change which fixes issue 8.0 Proposal: Remove WaitForConfirms and PublishBatch methods/APIs #963 )
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause an observable behavior change in existing systems)
• Documentation improvements (corrections, new content, etc)
• Cosmetic change (whitespace, formatting, etc)

Checklist

• I have read the CONTRIBUTING.md document
• I have signed the CA (see https://cla.pivotal.io/sign/rabbitmq)
• All tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in related repositories

Further Comments

Since we queue the publishes internally, there isn't really a need for a batch functionality. If a customer still wants it, it can easily built on top of the normal BasicPublish in customer code.