internal/pkg: move dependency flooding to cache

This imposes a hard upper limit to concurrency during dependency satisfaction and moves all dependency-related code out of individual implementations of Artifact. This change also includes ctx and msg as part of Cache.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/net.go

@@ -6,7 +6,6 @@ import (
 	"io"
 	"net/http"
 	"sync"
-	"syscall"
 )
 
 // An httpArtifact is an [Artifact] backed by a [http] url string. The method is
@@ -100,14 +99,9 @@ func (a *httpArtifact) do() (data []byte, err error) {
 	return
 }
 
-// Cure returns syscall.ENOTSUP. Callers should use Data instead.
-func (a *httpArtifact) Cure(*CureContext) error {
-	return syscall.ENOTSUP
-}
-
-// Data completes the http request and returns the resulting response body read
+// Cure completes the http request and returns the resulting response body read
 // to EOF. Data does not interact with the filesystem.
-func (a *httpArtifact) Data() (data []byte, err error) {
+func (a *httpArtifact) Cure() (data []byte, err error) {
 	a.mu.Lock()
 	defer a.mu.Unlock()