Added tier parameter to plugin RPC target BucketId

Move vshard related fields from _pico_property to _pico_tier
and adapt it in governor algorithm

Georgy Moshkin authored 8 months ago and Yaroslav Dynnikov committed 8 months ago

This fixes the A-B-A problem which was observed in the issue
https://git.picodata.io/picodata/picodata/picodata/-/issues/763.

Closes #763

- 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)

- Now we explicitly store the current & target vshard configuration in
  global storage