feat(domain_set): load geosite dat files by tag

[marstion]

Summary

Add domain_set support for loading selected tags from v2fly GeoSite-format files, including domain-list-community's dlc.dat.

Example:

- tag: geosite_cn
  type: domain_set
  args:
    geosite:
      - file: ./dlc.dat
        tags:
          - cn

Changes

• Add the geosite source configuration to domain_set.
• Decode the required GeoSite protobuf wire format without adding the full v2fly-core dependency.
• Load only explicitly requested tags.
• Map GeoSite domain types to existing matchers:
  • Plain → keyword
  • Regex → regexp
  • RootDomain → domain
  • Full → full
• Return clear errors for empty/missing tags, malformed data, and unsupported rule types.
• Preserve existing text-based files behavior.
• Add unit tests for rule conversion, tag filtering, missing tags, malformed data, and file loading.

AI assistance disclosure

This change was implemented with assistance from OpenAI Codex. The AI helped inspect the existing codebase, design the GeoSite parsing approach, write the implementation and unit tests, and run the test suite. The resulting changes were reviewed and validated locally.