fix[react-devtools]: fixed timeline profiler tests (#31261)

Fixes tests against React 18 after
#31154:
- Set `supportsTimeline` to true for `Store`.
- Execute `store.profilerStore.startProfiling` after `legacyRender`
import, because this is where `react-dom` is imported and renderer is
registered. We don't yet propagate `isProfiling` flag to newly
registered renderers, when profiling already started see:

https://github.com/facebook/react/blob/d5bba18b5d81f234657586865248c5b6849599cd/packages/react-devtools-shared/src/hook.js#L203-L204

packages/react-devtools-shared/src/__tests__/TimelineProfiler-test.js

@@ -1280,13 +1280,13 @@ describe('Timeline profiler', () => {
     });
 
     describe('when profiling', () => {
-      beforeEach(() => {
-        utils.act(() => store.profilerStore.startProfiling());
-      });
-
       describe('with legacy render', () => {
         const {render: legacyRender} = getLegacyRenderImplementation();
 
+        beforeEach(() => {
+          utils.act(() => store.profilerStore.startProfiling());
+        });
+
         // @reactVersion <= 18.2
         // @reactVersion >= 18.0
         it('should mark sync render without suspends or state updates', () => {
@@ -1537,6 +1537,10 @@ describe('Timeline profiler', () => {
 
         const {render: modernRender} = getModernRenderImplementation();
 
+        beforeEach(() => {
+          utils.act(() => store.profilerStore.startProfiling());
+        });
+
         it('should mark concurrent render without suspends or state updates', () => {
           utils.act(() => modernRender(<div />));
 

packages/react-devtools-shared/src/__tests__/setupTests.js

@@ -256,7 +256,9 @@ beforeEach(() => {
     },
   });
 
-  const store = new Store(((bridge: any): FrontendBridge));
+  const store = new Store(((bridge: any): FrontendBridge), {
+    supportsTimeline: true,
+  });
 
   const agent = new Agent(((bridge: any): BackendBridge));
   const hook = global.__REACT_DEVTOOLS_GLOBAL_HOOK__;