internal/core/dep: support dynamic dependencies

This mix of evaluation interleaved with conjunction
tracking seems most desirable for workflow
dependencies.

Change-Id: I61c8fbbc71139550613b0bf5c65e4351053eaebc
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/7641
Reviewed-by: CUE cueckoo <cueckoo@gmail.com>
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
diff --git a/internal/core/dep/testdata/list.txtar b/internal/core/dep/testdata/list.txtar
index 217194a..3ae09ce 100644
--- a/internal/core/dep/testdata/list.txtar
+++ b/internal/core/dep/testdata/list.txtar
@@ -9,3 +9,6 @@
 -- out/dependencies/all --
 d
 e
+-- out/dependencies/dynamic --
+d
+e