Fix EP post merge (#43730)
* restore
* add all reduce for ep
* fix init and bias sharding
* fix finalize weight init
* add full stacktracing
* fix
* okay big improvement here
* the only case shard index should be used is when we are acctually collecting for mergeModuleList
* more fixes
* fix EP forward gpt oss
* revert some shit
* when you are stupid sometimes you really need a brain :) :) :) :)
* fix TP
* Ok GPT oss is fixed now
* try to fix perms
* attempt to fix
* am I a doomer and AI is not that bad?
* fix
* it "passes" but the output is shit
* style my man
* outputs are gonna be giberish but at least the forward pass "works"
* dtyle
* fix mixtral
* okay shape fixes
* tensor idx is only for groupped gemm / EP
* fix gate_up shard
* fix :)
* revert some EP changes that are breaking other stuff
* style
* use moe_tp_experts
* revert unrelated, last nits and style
* good?
* fix modlar
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Co-authored-by: 3outeille <ferdinand.mom@epita.fr>
