src: support configurable snapshot
- Add support for --build-snapshot-config which allows passing snapshot configurations via a JSON configuration file.
- Add support for node::SnapshotConfig in the embedder API
The initial configurable options are:
- "builder" (SnapshotConfig::builder_script_path): path to the builder script.
- "withoutCodeCache" (SnapshotFlags::kWithoutCodeCache): disable code cache generation.