Implement a command that launches the application, runs a series of steps (a "workflow"), writes a profile to a file, and exits.
See: [#181775808](https://www.pivotaltracker.com/story/show/181775808)
# Important Notes
- The command to capture run and profile is used like: `./run profile --workflow=new_project --save-profile=out.json`. Defining some more workflows (collapse nodes, create node and edit value) comes next; they are implemented with the same infrastructure as the integration-tests.
- The `--save-profile` option can also be used when profiling interactively; when the option is provided, capturing a profile with the hotkey will write a file instead of dumping the data to the devtools console.
- If the IDE panics, the error message is now printed to the console that invoked the process, as well as the devtools console. (If a batch workflow fails, this allows us to see why.)
- New functionality (writing profile files, quitting on command, logging to console) relies on Electron APIs. These APIs are implemented in `index.js`, bridged to the render process in `preload.js`, and wrapped for use in Rust in a `debug_api` crate.
* profiling instrumentation
* Support native testing with mock impl of `mod js`
* Add benchmarks
* Wrapper: support methods.
* `#[profile]`: work in any context
* feature-gate lineno info that breaks IDE
* Support async; more docs; add perf analysis
* docs & formatting
