This also changes timeout error format to
"page.click: Timeout 5000ms exceeded", so that all errors
can be similarly prefixed with api name.
We can now have different api names in different clients,
and our protocol is more reasonable.
We now use a few helper.waitForEvent calls to wait for internal
events kNavigationEvent and kLifecycleEvent. With these events,
we should be able to replicate logic over rpc.
A progress roughly corresponds to an api call. It is used:
- to collect logs related to the call;
- to handle timeout;
- to provide "cancellation token" behavior so that cancelable process can either
early-exit with progress.throwIfCanceled() or race against it with progress.race();
- to ensure resources are disposed in the case of a failure
with progress.cleanupWhenCanceled();
- (possibly) to log api calls if needed;
- (in the future) to augment async stacks.
