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/incomplete.txtar b/internal/core/dep/testdata/incomplete.txtar
index fdf83ad..f22b60b 100644
--- a/internal/core/dep/testdata/incomplete.txtar
+++ b/internal/core/dep/testdata/incomplete.txtar
@@ -18,3 +18,10 @@
 e
 c.d
 c.d
+-- out/dependencies/dynamic --
+c.d
+c
+c
+e
+c.d
+c.d