Add a CLI option for selecting the naming strategy

[czechboy0]

Motivation

The recently introduced naming strategy is only configurable in the config file, but pure CLI users might also want to use it without creating a config file.

Modifications

Add a --naming-strategy option to the swift-openapi-generator CLI.

Result

Users can use the new naming strategy without creating a config file, if they didn't have one before.

Test Plan

Tested manually on a sample project.