[Scheduler][www] Put profiling feature behind flag (#16757)

Our infra currently doesn't support loading a separate profiling
build of Scheduler. Until that's fixed, the recommendation is to load
a single build and gate the profiling feature behind a flag.

Alternative to #16659

packages/scheduler/src/forks/SchedulerFeatureFlags.www.js

@@ -9,7 +9,8 @@
 export const {
   enableIsInputPending,
   enableSchedulerDebugging,
+  enableProfiling: enableProfilingFeatureFlag,
 } = require('SchedulerFeatureFlags');
 
-export const enableProfiling = __PROFILE__;
+export const enableProfiling = __PROFILE__ && enableProfilingFeatureFlag;
 export const enableMessageLoopImplementation = true;