Unify launch methods

[jorgepiloto]

Problem

PySTK is able to launch:

• STKDesktop
• STKEngine
• STKRuntime

Right now, each one requires its own import and options. This differs from other libraries, which usually provide the following user experience:

from ansys.product import launch_product

product = launch_product(...)
...
product.close()

Solution

The ecosystem is adopting ansys-common-tools as the way to unify the user experience. This library provides utilities to ease the implementation of product launchers.

We could implement this as an extension. This way, the ansys.stk.core can remain dependency free and users can still use the current STK{Desktop,Engine,Runtime} objects.