doc: comprehensive rename configuration guide with examples

[mcepl]

• Add detailed JSON configuration example for enabling pylsp-rope rename
• Clarify differences between rename plugins (pylsp_rope vs rope_rename vs jedi_rename)
• Include verification steps and current limitations
• Add comprehensive test suite demonstrating configuration patterns
• Document future benefits of using pylsp-rope's rename functionality

Fixes: https://github.com/python-rope/pylsp-rope/issues/29