feat: add LoadIncrementalFilteredPolicy() API for incremental filtered policy loading

[Copilot]

Fix: #387

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[hsluoyz]

@copilot for code and test code, need to refer to Golang Casbin as much as possible: apache/casbin#582

[Copilot]

@copilot for code and test code, need to refer to Golang Casbin as much as possible: apache/casbin#582

Refactored to match the Golang pattern from PR #582 (commit e7e7989):

Key changes to align with Golang architecture:

• Removed separate adapter methods (LoadIncrementalFilteredPolicy from IFilteredAdapter)
• Created shared internal method LoadFilteredPolicyInternal (similar to Golang's loadFilteredPolicy)
• LoadFilteredPolicy now calls ClearPolicy() before loading (matches Golang's model.ClearPolicy())
• LoadIncrementalFilteredPolicy directly calls the shared method without clearing
• Both methods now use the same underlying logic, differing only in whether they clear first

This matches the pattern where Golang has one adapter method and the clearing happens at the enforcer/model level, not in the adapter.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com/repos/casbin/casbin/pulls/582/files
  • Triggering command: curl -s REDACTED (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[github-actions]

🎉 This PR is included in version 2.19.0 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀