increase subsharding for Windows build_tests from 8 to 9 (flutter#158146)

Helps with flutter#157845. See that thread for more info.

<details>

<summary> Pre-launch checklist </summary> 

</details>

Author: andrewkolos

.ci.yaml

@@ -5415,7 +5415,8 @@ targets:
         ["devicelab", "hostonly", "mac", "arm64"]
       task_name: run_release_test_macos
 
-  - name: Windows build_tests_1_8
+  - name: Windows build_tests_1_9
+    bringup: true
     recipe: flutter/flutter_drone
     timeout: 60
     properties:
@@ -5429,11 +5430,12 @@ targets:
           {"dependency": "vs_build", "version": "version:vs2019"}
         ]
       shard: build_tests
-      subshard: "1_8"
+      subshard: "1_9"
       tags: >
         ["framework", "hostonly", "shard", "windows"]
 
-  - name: Windows build_tests_2_8
+  - name: Windows build_tests_2_9
+    bringup: true
     recipe: flutter/flutter_drone
     timeout: 60
     properties:
@@ -5447,11 +5449,12 @@ targets:
           {"dependency": "vs_build", "version": "version:vs2019"}
         ]
       shard: build_tests
-      subshard: "2_8"
+      subshard: "2_9"
       tags: >
         ["framework", "hostonly", "shard", "windows"]
 
-  - name: Windows build_tests_3_8
+  - name: Windows build_tests_3_9
+    bringup: true
     recipe: flutter/flutter_drone
     timeout: 60
     properties:
@@ -5465,11 +5468,12 @@ targets:
           {"dependency": "vs_build", "version": "version:vs2019"}
         ]
       shard: build_tests
-      subshard: "3_8"
+      subshard: "3_9"
       tags: >
         ["framework", "hostonly", "shard", "windows"]
 
-  - name: Windows build_tests_4_8
+  - name: Windows build_tests_4_9
+    bringup: true
     recipe: flutter/flutter_drone
     timeout: 60
     properties:
@@ -5483,11 +5487,12 @@ targets:
           {"dependency": "vs_build", "version": "version:vs2019"}
         ]
       shard: build_tests
-      subshard: "4_8"
+      subshard: "4_9"
       tags: >
         ["framework", "hostonly", "shard", "windows"]
 
-  - name: Windows build_tests_5_8
+  - name: Windows build_tests_5_9
+    bringup: true
     recipe: flutter/flutter_drone
     timeout: 60
     properties:
@@ -5501,11 +5506,12 @@ targets:
           {"dependency": "vs_build", "version": "version:vs2019"}
         ]
       shard: build_tests
-      subshard: "5_8"
+      subshard: "5_9"
       tags: >
         ["framework", "hostonly", "shard", "windows"]
 
-  - name: Windows build_tests_6_8
+  - name: Windows build_tests_6_9
+    bringup: true
     recipe: flutter/flutter_drone
     timeout: 60
     properties:
@@ -5519,11 +5525,31 @@ targets:
           {"dependency": "vs_build", "version": "version:vs2019"}
         ]
       shard: build_tests
-      subshard: "6_8"
+      subshard: "6_9"
+      tags: >
+        ["framework", "hostonly", "shard", "windows"]
+
+  - name: Windows build_tests_7_9
+    bringup: true
+    recipe: flutter/flutter_drone
+    timeout: 60
+    properties:
+      add_recipes_cq: "true"
+      dependencies: >-
+        [
+          {"dependency": "android_sdk", "version": "version:33v6"},
+          {"dependency": "chrome_and_driver", "version": "version:125.0.6422.141"},
+          {"dependency": "open_jdk", "version": "version:17"},
+          {"dependency": "goldctl", "version": "git_revision:2387d6fff449587eecbb7e45b2692ca0710b63b9"},
+          {"dependency": "vs_build", "version": "version:vs2019"}
+        ]
+      shard: build_tests
+      subshard: "7_9"
       tags: >
         ["framework", "hostonly", "shard", "windows"]
 
-  - name: Windows build_tests_7_8
+  - name: Windows build_tests_8_9
+    bringup: true
     recipe: flutter/flutter_drone
     timeout: 60
     properties:
@@ -5537,11 +5563,12 @@ targets:
           {"dependency": "vs_build", "version": "version:vs2019"}
         ]
       shard: build_tests
-      subshard: "7_8"
+      subshard: "8_9"
       tags: >
         ["framework", "hostonly", "shard", "windows"]
 
-  - name: Windows build_tests_8_8
+  - name: Windows build_tests_9_9
+    bringup: true
     recipe: flutter/flutter_drone
     timeout: 60
     properties:
@@ -5555,7 +5582,7 @@ targets:
           {"dependency": "vs_build", "version": "version:vs2019"}
         ]
       shard: build_tests
-      subshard: "8_8"
+      subshard: "9_9"
       tags: >
         ["framework", "hostonly", "shard", "windows"]