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

flutter#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:
  flutter/flutter#64061

ci/dev/prod_builders.json

@@ -1,23 +1,27 @@
 {
    "builders":[
       {
-         "name":"Linux Host Engine",
+         "name":"Linux Android AOT Engine",
          "repo":"engine"
       },
       {
-         "name":"Linux Fuchsia",
+         "name":"Linux Android Debug Engine",
          "repo":"engine"
       },
       {
-         "name":"Linux Android AOT Engine",
+         "name":"Linux Host Engine",
          "repo":"engine"
       },
       {
-         "name":"Linux Android Debug Engine",
+         "name":"Linux Fuchsia",
          "repo":"engine"
       },
       {
-         "name":"Mac Host Engine",
+         "name":"Linux Fuchsia FEMU",
+         "repo":"engine"
+      },
+      {
+         "name":"Linux Web Engine",
          "repo":"engine"
       },
       {
@@ -28,6 +32,10 @@
          "name":"Mac Android Debug Engine",
          "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"
       }
    ]
 }