[ci] Increase iOS sharding (#3119)

The sharding setup here is intended to match flutter/plugin to prepare
for merging, and it's being changed (along with the names) in
flutter/plugins#7064

Author: stuartmorgan-g

.ci.yaml

@@ -66,51 +66,70 @@ targets:
       target_file: ios_build_all_packages.yaml
       channel: stable
 
-  # TODO(stuartmorgan): Remove "- packages" from all task names once
-  # flutter/plugins is merged into this repo and turned down; it's here only
-  # because names must be unique across all flutter repositories.
-  - name: Mac_arm64 ios_platform_tests_1_of_4 master - packages
+  - name: Mac_arm64 ios_platform_tests_shard_1 master
+    bringup: true # New task
+    recipe: packages/packages
+    timeout: 60
+    properties:
+      add_recipes_cq: "true"
+      version_file: flutter_master.version
+      target_file: ios_platform_tests.yaml
+      package_sharding: "--shardIndex 0 --shardCount 5"
+
+  - name: Mac_arm64 ios_platform_tests_shard_2 master
     bringup: true # New task
     recipe: packages/packages
     timeout: 60
     properties:
       add_recipes_cq: "true"
       version_file: flutter_master.version
       target_file: ios_platform_tests.yaml
-      package_sharding: "--shardIndex 0 --shardCount 4"
+      package_sharding: "--shardIndex 1 --shardCount 5"
 
-  - name: Mac_arm64 ios_platform_tests_2_of_4 master - packages
+  - name: Mac_arm64 ios_platform_tests_shard_3 master
     bringup: true # New task
     recipe: packages/packages
     timeout: 60
     properties:
       add_recipes_cq: "true"
       version_file: flutter_master.version
       target_file: ios_platform_tests.yaml
-      package_sharding: "--shardIndex 1 --shardCount 4"
+      package_sharding: "--shardIndex 2 --shardCount 5"
 
-  - name: Mac_arm64 ios_platform_tests_3_of_4 master - packages
+  - name: Mac_arm64 ios_platform_tests_shard_4 master
     bringup: true # New task
     recipe: packages/packages
     timeout: 60
     properties:
       add_recipes_cq: "true"
       version_file: flutter_master.version
       target_file: ios_platform_tests.yaml
-      package_sharding: "--shardIndex 2 --shardCount 4"
+      package_sharding: "--shardIndex 3 --shardCount 5"
 
-  - name: Mac_arm64 ios_platform_tests_4_of_4 master - packages
+  - name: Mac_arm64 ios_platform_tests_shard_5 master
     bringup: true # New task
     recipe: packages/packages
     timeout: 60
     properties:
       add_recipes_cq: "true"
       version_file: flutter_master.version
       target_file: ios_platform_tests.yaml
-      package_sharding: "--shardIndex 3 --shardCount 4"
+      package_sharding: "--shardIndex 4 --shardCount 5"
 
   # Don't run full platform tests on both channels in pre-submit.
-  - name: Mac_arm64 ios_platform_tests_1_of_4 stable - packages
+  - name: Mac_arm64 ios_platform_tests_shard_1 stable
+    bringup: true # New task
+    recipe: packages/packages
+    presubmit: false
+    timeout: 60
+    properties:
+      channel: stable
+      add_recipes_cq: "true"
+      version_file: flutter_stable.version
+      target_file: ios_platform_tests.yaml
+      package_sharding: "--shardIndex 0 --shardCount 5"
+
+  - name: Mac_arm64 ios_platform_tests_shard_2 stable
     bringup: true # New task
     recipe: packages/packages
     presubmit: false
@@ -120,9 +139,9 @@ targets:
       add_recipes_cq: "true"
       version_file: flutter_stable.version
       target_file: ios_platform_tests.yaml
-      package_sharding: "--shardIndex 0 --shardCount 4"
+      package_sharding: "--shardIndex 1 --shardCount 5"
 
-  - name: Mac_arm64 ios_platform_tests_2_of_4 stable - packages
+  - name: Mac_arm64 ios_platform_tests_shard_3 stable
     bringup: true # New task
     recipe: packages/packages
     presubmit: false
@@ -132,9 +151,9 @@ targets:
       add_recipes_cq: "true"
       version_file: flutter_stable.version
       target_file: ios_platform_tests.yaml
-      package_sharding: "--shardIndex 1 --shardCount 4"
+      package_sharding: "--shardIndex 2 --shardCount 5"
 
-  - name: Mac_arm64 ios_platform_tests_3_of_4 stable - packages
+  - name: Mac_arm64 ios_platform_tests_shard_4 stable
     bringup: true # New task
     recipe: packages/packages
     presubmit: false
@@ -144,9 +163,9 @@ targets:
       add_recipes_cq: "true"
       version_file: flutter_stable.version
       target_file: ios_platform_tests.yaml
-      package_sharding: "--shardIndex 2 --shardCount 4"
+      package_sharding: "--shardIndex 3 --shardCount 5"
 
-  - name: Mac_arm64 ios_platform_tests_4_of_4 stable - packages
+  - name: Mac_arm64 ios_platform_tests_shard_5 stable
     bringup: true # New task
     recipe: packages/packages
     presubmit: false
@@ -156,7 +175,7 @@ targets:
       add_recipes_cq: "true"
       version_file: flutter_stable.version
       target_file: ios_platform_tests.yaml
-      package_sharding: "--shardIndex 3 --shardCount 4"
+      package_sharding: "--shardIndex 4 --shardCount 5"
 
   ### macOS desktop tasks ###
   # macos-platform_tests builds all the packages on ARM, so this build is run
@@ -179,6 +198,9 @@ targets:
       target_file: mac_build_all_packages.yaml
       channel: stable
 
+  # TODO(stuartmorgan): Remove "- packages" from all task names once
+  # flutter/plugins is merged into this repo and turned down; it's here only
+  # because names must be unique across all flutter repositories.
   - name: Mac_arm64 macos_platform_tests master - packages
     bringup: true # New task
     recipe: packages/packages