[ExternalDP][RL] Make external DP support on EP and ETP

[MengqingCao]

What this PR does / why we need it?

Make external DP support on EP and ETP
fix #1396 #1154

How was this patch tested?

CI passed with new added test.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.

Project coverage is 27.23%. Comparing base (c30ddb8) to head (602e688).
Report is 135 commits behind head on main.

Files with missing lines	Patch %	Lines
vllm_ascend/distributed/parallel_state.py	0.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1384      +/-   ##
==========================================
- Coverage   27.39%   27.23%   -0.16%     
==========================================
  Files          56       56              
  Lines        6191     6209      +18     
==========================================
- Hits         1696     1691       -5     
- Misses       4495     4518      +23     

Flag	Coverage Δ
unittests	27.23% <0.00%> (-0.16%)	⬇️

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[MengqingCao]

This is ready for review @Yikun @wangxiyuan @ganyi1996ppo

[MengqingCao]

Will close after #1422 is backportted on main

[MengqingCao]

closing as done in #1681