Implementing ready function

[NavneetThekkumpat]

1. When the canvas published app is initialized >> there could be a delay in registration of published app JSSDK.
2. If the TestEngine functions including getAppStatus is executed it returns COMMAND NOT FOUND error >> which in turn is interpreted as published app Test Engine JSSDK not found >> though it is still in process.

PROPOSAL

• Call TestEngine ready function from TE before any other functions are executed. This way the rest of the functions >> registered (in the app side) before executing them.
• With this implementation, lifecycle of TE function execution would look like Run TE >> execute ready function successfully >> execute other function like getAppStatus..

We just need to make sure TE continue supporting old apps (back compatibility >> older apps won't have this new ready function).

SUPPORTING DIFFERENT SCENARIOS

1. Webplayer app and published app versions with no testEngineReady() >> Continue test execution.
2. Webplayer app version with testEngineReady() and published app with no testEngineReady() >> Continue test execution.
3. Webplayer app version with no testEngineReady() >> Continue test execution.
4. Webplayer and published app with testEngineReady() >> Continue if true returned, else appropriate error codes are thrown in this case and handled appropriately.

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] 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	91%	88%	924	✔
Summary	91% (2453 / 2682)	88% (559 / 636)	924	✔

Minimum allowed line rate is 85%