* gather with doc

* resolve comment

* polish

* polish

* code style

* polish doc

* add_test

* polish

* polish

* add test check

* add test check

* polish

* polish

* polish

* polish

* fix_time_out

* polish

* fix timeout

* fix_timeout

* polish

* polish

* polish

* polish

* polish

* clear ProcessGroupCustom manually

* fix bug

* fix bug

* move destroy ProcessGroup to ProcessGroupIdMap

* enable destroy to all device

* remove unused comments

* change to internal api

* Update process_group.cc

* Update process_group.cc

* refactor: use base class

* fix: incorrect deps

* fix: add missing header

* refactor: update class structures

* fix: bkcl typo

* fix: remove redundant def

* 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