* Add LIVEBOOK_SHUTDOWN_ENABLED
Previously we relied on code:get_mode(), but since
releases are starting in interactive mode to use
less memory, we need a clearer mechanism.
* Move shutdown feature check to Livebook.Config
Co-authored-by: Jonatan Kłosko <jonatanklosko@gmail.com>
* Automate searching and adding new dependencies
* Restructure runtime management
* Leave search restrictions up to the runtime
* Support predefined dependencies in Embedded runtime dependency search
* Use the embedded runtime for dependency search test
* Fix typo
* Use module for loading embedded runtime dependencies
* Improve naming
* Group all runtime messages under a common prefix
* Move output specification ot the Runtime protocol
* Update doc comments
* Livebook.Evaluator -> Livebook.Runtime.Evaluator
* Livebook.ContentLoader -> Livebook.Notebook.ContentLoader
* Livebook.UniqueTask -> Livebook.Utils.UniqueTask
* Add import/export delegates to Livebook.LiveMarkdown
* Serve iframes from another local port when running on http
* Use relative hostname in local iframe URL
* Simplify server start check
* Use random iframe port when Livebook runs on a random port
* Rename space/ to iframe/
* LivebookWeb.IframePlug -> LivebookWeb.IframeEndpoint
* Improve file select layout on long paths
* Automatically back up notebooks without a file
* Run formatter
* Add margin when there are no sections
* Add an informative note about autosave directory
* Store autosave path instead of file in the config
* Rename autosave dir to autosave path
* Fix insert mode escape on section headlines
* Show ellipsis on selected file too
* Always create the default directory
* Apply review comments
