Give a service's held state its own field and key, so main compiles again

#64/#65 and #66 each added Applied.Declared: a directory's declared owner and
mode (string) and a service's held state (*FoundUnit), both under the JSON key
"declared". The directory's is already on nodes, written by d28ca95, so it
keeps the name and key; the service's becomes DeclaredUnit, "declared_unit".
#66 never deployed, so no node holds a record under the new key.

internal/apply/plan.go

@@ -125,14 +125,14 @@ func Plan(d *declaration.Declaration, known store.State, origin string) []Step {
 			case f == nil:
 				step.Verb, step.Why = "forget", "no longer declared; recorded before the host kept what it "+
 					"found, so it is left as it is"
-			case orphan.Declared != nil && ((f.State == "running" && orphan.Declared.State == "stopped") ||
-				(f.Boot == "enabled" && orphan.Declared.Boot == "disabled")):
+			case orphan.DeclaredUnit != nil && ((f.State == "running" && orphan.DeclaredUnit.State == "stopped") ||
+				(f.Boot == "enabled" && orphan.DeclaredUnit.Boot == "disabled")):
 				// startUnitBack's words (novox/hq ADR 0269): what the mesh's declaration stopped goes back.
 				var back []string
-				if f.State == "running" && orphan.Declared.State == "stopped" {
+				if f.State == "running" && orphan.DeclaredUnit.State == "stopped" {
 					back = append(back, "started")
 				}
-				if f.Boot == "enabled" && orphan.Declared.Boot == "disabled" {
+				if f.Boot == "enabled" && orphan.DeclaredUnit.Boot == "disabled" {
 					back = append(back, "enabled at boot")
 				}
 				// A preview: whether it is still as the mesh held it is read when the removal runs, and a