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/field.txtar b/internal/core/dep/testdata/field.txtar
index e993bc3..42af863 100644
--- a/internal/core/dep/testdata/field.txtar
+++ b/internal/core/dep/testdata/field.txtar
@@ -21,3 +21,8 @@
 c
 c
 c
+-- out/dependencies/dynamic --
+pattern
+name
+c
+c