Add skp_generator shard to LUCI config (#81096)

dev/prod_builders.json

@@ -552,6 +552,12 @@
       "task_name": "flutter_plugins",
       "flaky": false
     },
+    {
+      "name": "Linux skp_generator",
+      "repo": "flutter",
+      "task_name": "linux_skp_generator",
+      "flaky": true
+    },
     {
       "name": "Mac build_aar_module_test",
       "repo": "flutter",

dev/try_builders.json

@@ -179,6 +179,13 @@
       "enabled": true,
       "run_if": ["dev/**", "packages/flutter_tools/**", "bin/**"]
     },
+    {
+      "name": "Linux skp_generator",
+      "repo": "flutter",
+      "task_name": "linux_skp_generator",
+      "enabled": true,
+      "run_if": ["dev/", "packages/flutter/", "bin/"]
+    },
     {
       "name": "Linux tool_tests_general",
       "repo": "flutter",