Add flag to enable react render tracker in sample apps(enable only under flag)

[PorterNan]

What

Add flag to enable react render tracker in sample apps Remove default rrt element in html page

Why

How Tested

Process & policy checklist

• [ ] I have updated the project documentation to reflect my changes if necessary.
• [ ] I have read the CONTRIBUTING documentation.

Is this a breaking change?

• [ ] This change causes current functionality to break.