[Write restricted dashboards] Enable feature by default (#246602)

## Summary

This PR enabled the Saved Objects Access Control feature by default in
non-serverless offerings. This feature is what powers write-restricted
dashboards.


### Testing

1. Start ES & KB normally
2. Log in as an admin user and add sample data
3. Navigate to Dashboards and open any of the sample dashboards
4. Click the share button and verify that the access mode options
appears in the share modal
5. Repeat the test but add `savedObjects.enableAccessControl: false` to
the Kibana config, and verify that the access mode does not appear in
the share modal
6. Remove `savedObjects.enableAccessControl: false` from the Kibana
config, start ES & KB in serverless mode, verify that the access mode
does not appear in the share modal

Note: a release note was already added in
#224552

---------

Co-authored-by: Ryan <ryan.godfrey@elastic.co>

Author: jeramysoucy

config/serverless.yml

@@ -301,3 +301,6 @@ xpack.genAiSettings:
 # Cross Project Search
 cps.enabled: true
 cps.cpsEnabled: false
+
+# Disable saved objects access control features (write-restricted dashboards)
+savedObjects.enableAccessControl: false

src/core/packages/saved-objects/base-server-internal/src/saved_objects_config.ts

@@ -82,7 +82,7 @@ const soSchema = schema.object({
     schema.boolean({ defaultValue: true }),
     schema.boolean({ defaultValue: false })
   ),
-  enableAccessControl: schema.boolean({ defaultValue: false }),
+  enableAccessControl: schema.boolean({ defaultValue: true }),
 });
 
 export type SavedObjectsConfigType = TypeOf<typeof soSchema>;

src/core/packages/saved-objects/base-server-internal/src/serialization/serializer.test.ts

@@ -18,7 +18,7 @@ const createMockedTypeRegistry = ({
   isNamespaceAgnostic,
   isSingleNamespace,
   isMultiNamespace,
-  accessControlEnabled = false, // default to false
+  accessControlEnabled = true, // default to true
 }: {
   isNamespaceAgnostic: boolean;
   isSingleNamespace: boolean;

src/core/packages/saved-objects/server-internal/src/saved_objects_service.test.ts

@@ -101,7 +101,7 @@ describe('SavedObjectsService', () => {
       return new BehaviorSubject({
         maxImportPayloadBytes: new ByteSizeValue(0),
         maxImportExportSize: 10000,
-        enableAccessControl: accessControlEnabled ?? false,
+        enableAccessControl: accessControlEnabled ?? true, // default to true
       });
     });
     return mockCoreContext.create({ configService, env });
@@ -406,18 +406,18 @@ describe('SavedObjectsService', () => {
     });
 
     describe('#isAccessControlEnabled', () => {
-      it('returns false by default', async () => {
+      it('returns true by default', async () => {
         const coreContext = createCoreContext({});
         const soService = new SavedObjectsService(coreContext);
         const { isAccessControlEnabled } = await soService.setup(createSetupDeps());
-        expect(isAccessControlEnabled()).toEqual(false);
+        expect(isAccessControlEnabled()).toEqual(true);
       });
 
-      it('can be set to true', async () => {
-        const coreContext = createCoreContext({ accessControlEnabled: true });
+      it('can be set to false', async () => {
+        const coreContext = createCoreContext({ accessControlEnabled: false });
         const soService = new SavedObjectsService(coreContext);
         const { isAccessControlEnabled } = await soService.setup(createSetupDeps());
-        expect(isAccessControlEnabled()).toEqual(true);
+        expect(isAccessControlEnabled()).toEqual(false);
       });
 
       describe('#setAccessControlTransforms', () => {