Run scenarios

### 🤔 What's the problem you're trying to solve?

I don't want to leave my editor to run scenarios

### ✨ What's your proposed solution?

A keyboard shortcut for running the scenario on the current line, or all the scenarios, or all the scenarios in a directory, or filtered by tags etc etc.

This would run Cucumber with the `message` formatter, send the messages to a temporary file, parse the contents of that file (using [this class](https://github.com/cucumber/message-streams/blob/main/src/NdjsonToMessageStream.ts)) and decorate lines in the code with a background indicating the status. Errors can be expanded straight in the editor. Stack trace elements would be links.

How to execute Cucumber depends on the Cucumber implementation, so the editor would have to know how to deal with each implementation. We should provide a setting to allow users to override how Cucumber is run.

Start by reviewing the proposed Cucumber message flow and the linked NdjsonToMessageStream class. Identify the extension entry points for keyboard shortcuts, scenario execution, temporary-file parsing, editor decorations, expandable errors, stack-trace links, and implementation-specific run settings. Done means agreeing on and implementing the required editor workflow across supported Cucumber implementations.

Written by the indexing model from the issue text.