feat(tvix/eval): implement builtins.filterSource

We add a new set of builtins called `import_builtins`, which
will contain import-related builtins, such as `builtins.path` and
`builtins.filterSource`. Both can import paths into the store, with
various knobs to alter the result, e.g. filtering, renaming, expected
hashes.

We introduce `filtered_ingest` which will drive the filtered ingestion
via the Nix function via the generator machinery, and then we register
the root node to the path info service inside the store.

`builtins.filterSource` is very simple, `builtins.path` is a more
complicated model requiring the same logic albeit more sophisticated
with name customization, file ingestion method and expected SHA-256.

Change-Id: I1083f37808b35f7b37818c8ffb9543d9682b2de2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10654
Autosubmit: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>

tvix/glue/Cargo.toml

@@ -20,6 +20,7 @@ thiserror = "1.0.38"
 serde = "1.0.195"
 serde_json = "1.0"
 sha2 = "0.10.8"
+walkdir = "2.4.0"
 
 [dependencies.wu-manber]
 git = "https://github.com/tvlfyi/wu-manber.git"
@@ -28,6 +29,7 @@ git = "https://github.com/tvlfyi/wu-manber.git"
 criterion = { version = "0.5", features = ["html_reports"] }
 hex-literal = "0.4.1"
 lazy_static = "1.4.0"
+nix = { version = "0.27.1", features = [ "fs" ] }
 pretty_assertions = "1.4.0"
 rstest = "0.18.2"
 tempfile = "3.8.1"