Use ArchTaskExecutor instead of InstantTaskExecutorRule

[skydoves]

Use ArchTaskExecutor instead of InstantTaskExecutorRule

@get:Rule
var instantTaskExecutorRule = InstantTaskExecutorRule()

The issue is that this one does not provide a real thread for main thread and accepts all threads as main; hence might hide some bugs by having a different behavior than the real implementation. (and it is likely to be deprecated - removed). by yigit.

Modified:

• removed InstantTaskExecutorRule
• added TaskExecutorUtils : registerTaskExecutor(), unRegisterTaskExecutor()

[XinyueZ]

@skydoves I think Google has updated the test framework internal already, could you check?

[XinyueZ]

@tiembo I think the newest google's repo has updated corresponded APIs.