feat: Allow full customization of runner images and periodically update them

[kichik]

Build images in AWS using CodeBuild (or any user configured method) so that:

1. We can automatically update images on a schedule to get the latest runner version and latest OS updates.
2. We can build any type of image independent of the deployment platform. This will make it easy to provide Windows or ARM images (closes More runner architectures #7).
3. We can expose an interface allowing the user to easily modify the Docker images by adding packages or commands to the build process (closes Runner image customization #26).

BREAKING CHANGE: providers no longer take runner version directly

[kichik]

See the updated readme for usage.

[sercantor]

Would it be more obvious to have a matching provider label for self-hosted.yml and the readme? Like:

// create a custom CodeBuild provider
const myProvider = new CodeBuildRunner(this, 'codebuild runner', { 
    label: 'codebuild-x64',
    ...
});
// grant some permissions to the provider
...

// create the runner infrastructure
new GitHubRunners(this, 'runners', {
    providers: [codebuild-x64],
});

I'm just suggesting it because there may be people copying from the readme and not seeing their workers running because the labels don't match when they run their workflow against self.hosted.yml. Also makes it obvious for people to see that there are options for architecture.

Again, it's just a suggestion 🤷

[kichik]

That's a good point. I keep forgetting to add proper workflow example. self-hosted.yml is not an ideal example. It's way too complex.

[sercantor]

great commit, it's definitely more readable now, thanks for all the work 👍