V11 - Event Migration to Envelopes -> GherkinSourceRead

[luke-hill]

Description

This is the first of many PR's that will aim to migrate out the complexity of MessageBuilder so that the raw events being emitted are that of Envelope's with the requisite info.

As such this will remove the need to emit events and then convert them.

This will see us create a series of #to_envelope methods in the requisite places here or in core

Type of change

Please delete options that are not relevant.

• Refactoring (improvements to code design or tooling that don't change behaviour)
• New feature (non-breaking change which adds new behaviour)

Please add an entry to the relevant section of CHANGELOG.md as part of this pull request.

Checklist:

Your PR is ready for review once the following checklist is
complete. You can also add some checks if you want to.

• Tests have been added for any changes to behaviour of the code
• New and existing tests are passing locally and on CI
• bundle exec rubocop reports no offenses
• RDoc comments have been updated
• CHANGELOG.md has been updated

[luke-hill]

ping @brasmusson