`main()` function used to be needed to support dart, since dart
Does not allow top level statements. Since we no longer use dart
The need for `main()` has been removed.
In preparation for `Basel` and standardized way of running tests
we are removing `main()`
PR Close#21053
`flush()` can now be used from within fakeAsync tests to simulate moving
time forward until all macrotask events have been cleared from the
event queue.
Kristiyan Kostadinov
Miško Hevery
Julie Ralph
Jason Aden