ci(mergify): clarify queue_conditions and merge_conditions (#9510)

`queue_conditions` prevent a PR from entering the merge queue. What we
really want is `merge_conditions`, which allows PRs to embark on the
merge train while integration tests are still running, and only actually
merge when the tests are successful.

Also, we can use `queue_conditions` to consolidate and clean up the
condition logic in our `pull_request_rules`.

https://docs.mergify.com/merge-queue/setup/#configuring-the-merge-queue-rules

Tested successfully in Agoric/mergify-experiements#13

.mergify.yml

@@ -6,6 +6,19 @@ queue_rules:
 
       {{ body | trim }}
     queue_conditions:
+      - base=master
+      - or:
+          - check-pending=integration-test-result
+          - check-success=integration-test-result
+          - label=bypass:integration
+      - or:
+          - and: # breakage succeeds like we thought
+              - check-success=breakage
+              - -label=proto:expect-breakage
+          - and: # breakage fails like we thought
+              - check-failure=breakage
+              - label=proto:expect-breakage
+    merge_conditions:
       - base=master
       # Require integration tests before merging only
       - or:
@@ -20,17 +33,6 @@ pull_request_rules:
       - or:
           - '#commits-behind=0'
           - label=bypass:linear-history
-      - or:
-          - check-pending=integration-test-result
-          - check-success=integration-test-result
-          - label=bypass:integration
-      - or:
-          - and: # breakage succeeds like we thought
-              - check-success=breakage
-              - -label=proto:expect-breakage
-          - and: # breakage fails like we thought
-              - check-failure=breakage
-              - label=proto:expect-breakage
     actions:
       queue:
         name: main
@@ -39,17 +41,6 @@ pull_request_rules:
     conditions:
       - base=master
       - label=automerge:rebase
-      - or:
-          - check-pending=integration-test-result
-          - check-success=integration-test-result
-          - label=bypass:integration
-      - or:
-          - and: # breakage succeeds like we thought
-              - check-success=breakage
-              - -label=proto:expect-breakage
-          - and: # breakage fails like we thought
-              - check-failure=breakage
-              - label=proto:expect-breakage
     actions:
       queue:
         name: main
@@ -59,17 +50,6 @@ pull_request_rules:
     conditions:
       - base=master
       - label=automerge:squash
-      - or:
-          - check-pending=integration-test-result
-          - check-success=integration-test-result
-          - label=bypass:integration
-      - or:
-          - and: # breakage succeeds like we thought
-              - check-success=breakage
-              - -label=proto:expect-breakage
-          - and: # breakage fails like we thought
-              - check-failure=breakage
-              - label=proto:expect-breakage
     actions:
       queue:
         name: main