[Scheduler][www] Put profiling feature behind flag

[acdlite]

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

[sizebot]

Details of bundled changes.

Comparing: 8f03109...752f223

scheduler

File	Filesize Diff	Gzip Diff	Prev Size	Current Size	Prev Gzip	Current Gzip	ENV
scheduler-tracing.profiling.min.js	0.0%	+0.3%	3.25 KB	3.25 KB	991 B	994 B	NODE_PROFILING
scheduler-unstable_mock.production.min.js	0.0%	🔺+0.1%	4.73 KB	4.73 KB	1.98 KB	1.98 KB	UMD_PROD
Scheduler-dev.js	+0.3%	+0.2%	29.62 KB	29.7 KB	7.52 KB	7.54 KB	FB_WWW_DEV
Scheduler-profiling.js	+3.7%	+2.3%	16.24 KB	16.84 KB	3.76 KB	3.85 KB	FB_WWW_PROFILING
scheduler-tracing.development.js	0.0%	+0.1%	11.72 KB	11.72 KB	3.03 KB	3.03 KB	NODE_DEV
scheduler-tracing.production.min.js	0.0%	🔺+0.3%	728 B	728 B	383 B	384 B	NODE_PROD
scheduler-unstable_mock.development.js	0.0%	0.0%	21.93 KB	21.93 KB	5.07 KB	5.07 KB	NODE_DEV
scheduler-unstable_mock.production.min.js	0.0%	🔺+0.1%	4.72 KB	4.72 KB	1.92 KB	1.92 KB	NODE_PROD
SchedulerMock-dev.js	+0.4%	+0.3%	22.25 KB	22.33 KB	5.15 KB	5.17 KB	FB_WWW_DEV
scheduler.development.js	0.0%	0.0%	29.16 KB	29.16 KB	7.43 KB	7.43 KB	NODE_DEV
scheduler.production.min.js	0.0%	0.0%	5 KB	5 KB	2 KB	2 KB	NODE_PROD

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