feat: Return launch and connection info from standalone launcher dry-run

[mkundu1]

Use case of the dry_run argument of the launch_fluent() to use with external launcher for launching Fluent in a different machine.

1. Assume a shared directory between the server machine (where Fluent is launched) and client machine (where PyFluent is run) is available at path /mnt/shared in the server machine and \\server\shared in the client machine.
2. Set the environment variable SERVER_INFO_DIR to /mnt/shared in the server machine and \\server\shared in the client machine.
3. In client, launch_fluent(fluent_path=<path to fluent exe as in the server machine>, dry_run=True) will return a tuple containing Fluent launch string and the absolute path of the server info file in client.
4. Fluent is launched by the external launcher using the Fluent launch string returned above.
5. In client, PyFluent connects using connect_to_fluent() with the server info file path returned above.