container: wrap container init start errors

This helps indicate the exact origin and nature of the error. This eliminates generic WrapErr from container.

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

internal/app/shim.go

@@ -65,7 +65,7 @@ func ShimMain() {
 		if errors.Is(err, syscall.EBADF) {
 			log.Fatal("invalid config descriptor")
 		}
-		if errors.Is(err, container.ErrNotSet) {
+		if errors.Is(err, container.ErrReceiveEnv) {
 			log.Fatal("HAKUREI_SHIM not set")
 		}