Builder: ask again an ask its stream can no longer answer, and give it tools to read and ask again (issue 1945)

A build ask its seat's stream gave up on, dropped or ended with no step was
waited for with no end, and on restart taken over and waited for again: no
build node would ever answer it, and nothing could ask it again (trunk key
of mesh-build-node at 4e7b118e, building since 19:06; seven keys at 18:44).

At the step bound, a context's bound and no timer of its own, the builder
reads what the bus says of an ask with no step: gone from its stream, or
first in line while a node took a later ask. Such an ask is asked again
under a new id the key names, logged and said as build.asked-again, at most
three askings, then the key fails with why. The bus's max-deliveries
advisory would tell it sooner, but the builder is granted neither it nor the
workers' information, and the controller is not changed here.

builder_stuck reads every waiting key with its asks, askings and steps;
builder_ask_again writes the new reasks state, which the builder watches
and answers.

modules/mesh-delivery-builder/module.json

@@ -2,6 +2,13 @@
   "module": "mesh-delivery-builder",
   "version": "1",
   "slug": "builder",
+  "tools": [
+    "builder_ask_again",
+    "builder_stuck"
+  ],
+  "emits": [
+    "build.asked-again"
+  ],
   "consumes": [
     "mesh-build-go.toolchain.reported",
     "mesh-build-node.toolchain.reported",
@@ -12,7 +19,8 @@
   ],
   "state": [
     { "name": "builds", "history": 5 },
-    { "name": "instances", "history": 1 }
+    { "name": "instances", "history": 1 },
+    { "name": "reasks", "history": 1 }
   ],
   "reads": [
     "mesh-build-go.steps",
@@ -78,6 +86,17 @@
         "system": "arch",
         "from": "cmd/mesh-delivery-builder",
         "binary": "mesh-delivery-builder"
+      },
+      {
+        "name": "tools",
+        "kind": "bundle",
+        "language": "go",
+        "system": "arch",
+        "from": "cmd/mesh-delivery-builder-tools",
+        "binary": "mesh-delivery-builder-tools",
+        "loads": [
+          "mesh-delivery-builder-tools"
+        ]
       }
     ]
   }