Event <-> Message conversion (Mapping Document)

### 🤔 What's the problem you've observed?

We need to generate a mapping of events to messages. Ideally in the situation to start with we can generate both directly from emmittence - but then eventually we can remove events

### ✨ Do you have a proposal for making it better?

# Event <-> Message 1:1 map
- `Envelope` <-> `Envelope`
- `GherkinSourceRead` <-> `Source`
- `StepDefinitionRegistered` <-> `StepDefinition`
- `TestCaseReady` <-> `TestCase` (With `n` nested `TestStep`)
- `TestCaseStarted` <-> `TestCaseStarted`
- `TestCaseFinished` <-> `TestCaseFinished` (With `:will_be_retried` attribute derived from combination of event AND repository object)
- `TestRunStarted` <-> `TestRunStarted`
- `TestRunFinished` <-> `TestRunFinished` (With `:success` attribute derived from event)
- `TestRunHookStarted` <-> `TestRunHookStarted`
- `TestRunHookFinished` <-> `TestRunHookFinished` (With nested `TestStepResult`)
- `TestStepStarted` <-> `TestStepStarted`
- `TestStepFinished` <-> `TestStepFinished` (With nested `TestStepResult`)
- `UndefinedParameterType` <-> `UndefinedParameterType`

# Event -> No Message 1:0 map
- `GherkinSourceParsed`
- `HookTestStepCreated`
- `StepActivated`
- `TestStepCreated`

# Unhandled events (No listener in `MessageBuilder`)
- `TestCaseCreated`

### 📚 Any additional context?

_No response_