* refactor: replace Collective & PointToPoint with NCCLEnv

* refactor: rename to RunFnInNCCLEnv

* refactor: pass std::function by value

* refactor: simplify send, recv interfaces

* refactor: rm send_partial, recv_partial, all_gather_partial

* refactor: send, recv, send_partial, recv_partial

* refactor: rm useless const ref

* fix no sync bugs

* update

* update task chain

fix: update wait chain

feat: add `GetDeviceContext` for gloo

* fix oom

* fix dev

* update

* update
Co-authored-by: NLiYuRio <liyuruijx@163.com>
Co-authored-by: NForFishes <2282912238@qq.com>

* fix conflict

* new pg apis

* add docs of new apis

* update

* fix coverage

* update

* fix bug

* fix reduce scatter

* fix api

* update
Co-authored-by: NForFishes <2282912238@qq.com>

* fix alltoall

* rename utest

* add processgroup_nccl