Follow config from a durable consumer, compose again only what changed since, and hold the node only for a write (issue 1945, ADR 0545, review)

The start composed every kept composition of every module on every node, each a
whole node composed in memory under the node's lock: 10 to 50 minutes at a
start, holding take-ins back. Now the writes of mesh-config_resolved are read
from the durable consumer mesh-controller-config-follow, acknowledged once the
change is composed, so a restart composes again only what was written since
the last change handled, and a first start nothing it did not hear. The node's
lock is taken for each write alone. A consumer that cannot be made or read
raises config-not-followed and is tried again a minute later, cleared once it
reads. The controller's account is granted that consumer's acknowledgements
where mesh-config serves, as its verb is.
Research 072: milestone 2, the composer reacting to the change of an input.

cmd/mesh-controller/plain_words.go

@@ -84,6 +84,13 @@ var plainWordings = map[string]func(conditions.Observation) words{
 				"builds announced there wait until the controller starts again. The details say which and why.",
 			Resolved: "the mesh reads where new builds are announced again"}
 	}),
+	// Config not followed into the compositions (kept_compositions.go, novox/hq ADR 0545).
+	kindConfigNotFollowed: worded(func(o conditions.Observation) words {
+		return words{Headline: "Changes of settings are not reaching the machines",
+			Explanation: "The mesh could not read the settings as they change, so a changed setting is not prepared for " +
+				"the machines until it can. It tries again every minute; the details say why.",
+			Resolved: "changes of settings reach the machines again"}
+	}),
 	// Machines and their node-engine.
 	"silent": worded(func(o conditions.Observation) words {
 		m := machineOr(o, "a machine")