Adds all the engine builders to the file used to validate tree status. (#20642)

Builders are read from a json file to get their last builds using
buildbucket and calculate the tree status. Some builders were not being
used for the tree status validation allowing rollers to land changes
even though some builders were failing.

Bug:
  https://github.com/flutter/flutter/issues/64061
diff --git a/ci/dev/prod_builders.json b/ci/dev/prod_builders.json
index 58fc27c..435046d 100644
--- a/ci/dev/prod_builders.json
+++ b/ci/dev/prod_builders.json
@@ -1,14 +1,6 @@
 {
    "builders":[
       {
-         "name":"Linux Host Engine",
-         "repo":"engine"
-      },
-      {
-         "name":"Linux Fuchsia",
-         "repo":"engine"
-      },
-      {
          "name":"Linux Android AOT Engine",
          "repo":"engine"
       },
@@ -17,7 +9,19 @@
          "repo":"engine"
       },
       {
-         "name":"Mac Host Engine",
+         "name":"Linux Host Engine",
+         "repo":"engine"
+      },
+      {
+         "name":"Linux Fuchsia",
+         "repo":"engine"
+      },
+      {
+         "name":"Linux Fuchsia FEMU",
+         "repo":"engine"
+      },
+      {
+         "name":"Linux Web Engine",
          "repo":"engine"
       },
       {
@@ -29,6 +33,10 @@
          "repo":"engine"
       },
       {
+         "name":"Mac Host Engine",
+         "repo":"engine"
+      },
+      {
          "name":"Mac iOS Engine",
          "repo":"engine"
       },
@@ -41,12 +49,20 @@
          "repo":"engine"
       },
       {
-         "name":"Windows Host Engine",
+         "name":"Mac Web Engine",
          "repo":"engine"
       },
       {
          "name":"Windows Android AOT Engine",
          "repo":"engine"
+      },
+      {
+         "name":"Windows Host Engine",
+         "repo":"engine"
+      },
+      {
+         "name":"Windows Web Engine",
+         "repo":"engine"
       }
    ]
 }