Create sim templates in parallel when clone simulator feature is enabled

[ravimandala]

Whether the simulator cloning is an optional feature or default behavior, the creating of sim templates should be done in parallel. It is very important to cut down on this time since the time spent in creating sim templates is the time that is not spent spawning the simulators and running the tests.
\cc @ob

[ob]

How many sim templates are there typically?

[ravimandala]

It's usually one for each type of app using across all the input test bundles. For example, scenario tests might use one version of the app and app-hosted unit tests might use a different app.

Also, the template name needs to be different for different apps to completely support this.

[chenxiao0228]

@ravimandala any updates?