Param offset in _ParamAndGradBucket should be aligned

[skydoorkai]

What does this PR do ?

param_to_index in _ParamAndGradBucket would be used when mxfp8 primary weight is set by fp8_param_gather.
The param offset should be aligned to 64 if distributed optimizer is used. Otherwise, if there are params whose numel is not 64-aligned, finish_param_sync would copy incorrect weights for mxfp8 primary weight as (param_start, param_end) are incrrect.

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[BestJuly]

Hi @skydoorkai , thanks for the PR. Can you please help review this commit change which adds a UT to guard this case, so that I can make it into dev branch quickly. And then I can help accelerate the process of this PR.

[skydoorkai]

Hi @skydoorkai , thanks for the PR. Can you please help review this commit change which adds a UT to guard this case, so that I can make it into dev branch quickly. And then I can help accelerate the process of this PR.

Reviewed that dev PR.

[BestJuly]

/ok to test 97edd35

[ericharper]

/ok to test d00eb7b

[Phlip79]

/ok to test d061188