Migrate fuchsia_precache to shard tests. (#139202)

Adhoc tests are being deprecated and existing tests are being migrated to shard tests.

Bug: https://github.com/flutter/flutter/issues/139153

.ci.yaml

@@ -681,8 +681,7 @@ targets:
     recipe: flutter/flutter
     timeout: 60
     properties:
-      validation: fuchsia_precache
-      validation_name: Fuchsia precache
+      shard: fuchsia_precache
       tags: >
         ["framework", "hostonly", "shard", "linux"]
 

dev/bots/test.dart

@@ -265,6 +265,7 @@ Future<void> main(List<String> args) async {
       'realm_checker': _runRealmCheckerTest,
       'customer_testing': _runCustomerTesting,
       'analyze': _runAnalyze,
+      'fuchsia_precache': _runFuchsiaPrecache,
       kTestHarnessShardName: _runTestHarnessTests, // Used for testing this script; also run as part of SHARD=framework_tests, SUBSHARD=misc.
     });
   } catch (error, stackTrace) {
@@ -1602,6 +1603,31 @@ Future<void> _runAnalyze() async {
   );
 }
 
+// Runs flutter_precache.
+Future<void> _runFuchsiaPrecache() async {
+  printProgress('${green}Running flutter precache tests$reset');
+  await runCommand(
+    'flutter',
+    <String>[
+      'config',
+      '--enable-fuchsia',
+    ],
+    workingDirectory: flutterRoot,
+  );
+  await runCommand(
+    'flutter',
+    <String>[
+      'precache',
+      '--flutter_runner',
+      '--fuchsia',
+      '--no-android',
+      '--no-ios',
+      '--force',
+    ],
+    workingDirectory: flutterRoot,
+  );
+}
+
 /// Runs the skp_generator from the flutter/tests repo.
 ///
 /// See also the customer_tests shard.