This change migrates plugin config format away from using JSON to use
TOML.
- Addresses the plugin portion of discussion #1336
## Type of Change
- [ ] Bug fix
- [X] New feature
- [ ] Breaking change
- [ ] Documentation update
## Motivation and Context
Context within https://github.com/apple/container/discussions/1336
> We're looking to improve the user experience and overall functionality
of setting defaults for container to better enable future use cases.
>
> Today container uses macOS's
[UserDefaults](https://developer.apple.com/documentation/foundation/userdefaults)
to configure settings needed at runtime. As mentioned in
https://github.com/apple/container/issues/608, UserDefaults may be
idiomatic for macOS, but they apply globally to all sessions and do not
handle representing complex, hierarchical data well. Additionally, we
currently have two ways of setting these defaults, either directly with
macOS's defaults command or through container system property.
>
> https://github.com/apple/container/issues/608 proposes moving to use
environment variables in place of UserDefaults. However, we do not
believe this is sufficient. Environment variables are not in a
consistent location, are not sourced from data, and also do not handle
representing complex, hierarchical data well.
As part of this migration to TOML for user settings we want to also move
plugin settings to use TOML so that we can have a singular file format
for `container` configurations.
## Testing
- [X] Tested locally
- [X] Added/updated tests
- [ ] Added/updated docs
- Sets up API server as source of truth for installation root, similarly
to what was done for the data root. `system start` establishes the
install root, setting the environment variable `CONTAINER_INSTALL_ROOT`
when launching the API server.
- The API server propagates the environment variable when launching
helpers, and returns the install root to the CLI via the health check
XPC.
- Includes several fixes for detecting plugins that use app bundle
layout.
Noah Thornton