TestEngine JS Feature Gate

[landonmsft]

Description

Feature switch created in Test Engine to switch between serverside JS implementation and TestEngine JS implementation. Query Params are created and passed when switch is turned on.

Checklist

• [x] The code change is covered by unit tests. I have added tests that prove my fix is effective or that my feature works
• [x] I have performed end-to-end test locally.
• [x] New and existing unit tests pass locally with my changes
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I used clear names for everything
• [x] I have performed a self-review of my own code

[github-actions[bot]]

Package	Line Rate	Branch Rate	Complexity	Health
Microsoft.PowerApps.TestEngine	94%	91%	819	✔
Summary	94% (2187 / 2317)	91% (519 / 570)	819	✔

Minimum allowed line rate is 50%