YQL-19747: Refactor sql/v1/complete usage of Future and Ptr

- [x] Chained futures, add `CompleteAsync` method (then will migrate the YDB CLI on it).
- [x] Removed deadlined and fallback NameService as unused
- [x] Annotate thread-safe methods with `const` and use `AtomicSharedPtr` for them.
- [x] Move `name` to `name/service` with backward compatibility with the YDB CLI.

---

`CompletionEngine` is left thread-unsafe because of the dependency chain `CompletionEngine -> LocalSyntaxAnalysis -> C3Engine` which is thread-unsafe, but readonly indexed data structures such as `Ranking` and `NameService` are annotated with const and distributed via shared pointers.

I removed deadlined and fallback name services because the first is stupid the second is ahead of its time and is better to be added later to keep interfaces as minimal as possible.

---

The migration on async complete plan:
1. Introduce CompleteAsync
2. Migrate clients on CompleteAsync
3. Make Complete to return Future
4. Migrate clients on Complete
5. Remove CompleteAsync

---

- Related to https://github.com/ydb-platform/ydb/issues/9056
- Related to https://github.com/vityaman/ydb/issues/33
- Related to https://github.com/vityaman/ydb/issues/31

---

Pull Request resolved: https://github.com/ytsaurus/ytsaurus/pull/1241

Co-authored-by: vvvv <vvvv@yandex-team.com>
Co-authored-by: vvvv <vvvv@yandex-team.com>
commit_hash:497cc081ab78bebf7354e0acfaa418d936cc8240

0 files changed, 0 insertions, 0 deletions