plugin rpc sdk

Summary

1. feat: allow calling static picodata procs using .proc syntax

   Use "/path" RPC routes to call plugin-defined endpoints. Use ".proc" RPC routes to call builtin picodata endpoints (for example .proc_instance_info)

2. feat: introduce picoplugin::transport::rpc module

   • use RouteBuilder to register rpc endpoints (input and ouptut is raw bytes for now)
   • use RequestBuilder to send RPC requests to other instances which are running a specified plugin.service (guarded by version)
     • supported routing by
       • explicit instance_id
       • replicaset_id
       • bucket_id
       • any available instance with given service
   • use context::Context to extract information about request or add custom fields at runtime (middleware not yet implemented)

3. chore: add a internal_tests feature in picoplugin for unit tests

4. test: set fiber name in internal tests

5. refactor: make a ConnectionPool for plugins

6. fixup extract stop_service

7. feat: add plugin_name, service_name & service_version to PicoContext

8. refactor: extract stop_service function

9. feat: introduce picoplugin::util::FfiSafeStr for simple string passing over ffi

10. fix: allow sending ?Sized types and receiving RawBytesBuf via ConnectionPool

11. debug: table.keys & table.values utility functions

12. chore: tweak traft::Error::NoSuchInstance

13. feat: add _pico_replicaset_uuid index to _pico_replicaset table

14. chore: clippy warning

15. feat: introduce custom picodata specific error codes for BoxError

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• Close #693 (closed)
• Changes should be cherry-picked to 24.2: no
• Docs follow-up:
  • schema changes: docs#302 (closed)
  • plugin sdk: docs#282 (closed)