Implement compression of objects before they are saved into the storage
provider. Each container type can specify which algorithm to use
(currently `none` or `zstd`) and the compression level.
Make the issuing of notification completely out of band with respect to
the `Pipeline`. Now the `StorageProvider` is responsible for providing
notifications to clients. Since some providers are local-only, there is
a `LOCAL_QUEUE` which allows sensing notifications through a local
queue, re-using the local revng daemon.
Add an additional piece of metadata that states which pipes are used to
compute a specific artifact. This can be used to derive which
configuration options influence the creation of an artifact.
Add two additional fields to `Artifact`: `defined_locations` and
`preferred_artifacts`. These are pieces of metadata that allow
navigation between multiple PTML-enabled documents.
Add categories in the pipeline, allow an artifact to have a category
specified which allows it to be shown or hidden by default. Adapt the
CLI tools to hide artifacts of the category that don't
`show_by_default=True`.
Rework which information is transmitted in the pipeline metadata,
avoiding redundancy and moving some information there instead of
returning it every time a request is made.
Giacomo Vercesi