Remove fp8 model init context because it is handled by MCORE

[guyueh1]

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What does this PR do ?

Remove wrapping GPT model initialization in TE fp8_model_init context, because MCORE has wrapped the initialization of each layer in proper context already.

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[chtruong814]

The llama4 tests failed because this PR needed to merge with main to get a fix for those tests. If those are the only tests that failed, then I'm ok merging this after the PR receives an approval.

[guyueh1]

This PR needs further work to handle two cases: mcore_gpt = True or False. Change this to draft until that's fixed.

[guyueh1]

@timmoon10 can you review?

[ko3n1g]

CI is ready, let us know when to merge