Reimplemented partial split download support (revival of #6832)

[ArjunJagdale]

(revival of #6832)

#7648 (comment)

Close #4101, and more

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PR under work!!!!

[ArjunJagdale]

Mario’s Patch (in PR #6832):

def _make_split_generators_kwargs(self, prepare_split_kwargs):
    # Pass `pipeline` into `_split_generators()` from `prepare_split_kwargs` if
    # it's in the call signature of `_split_generators()`.
    # This allows for global preprocessing in beam.
    split_generators_kwargs = {}
    if "pipeline" in inspect.signature(self._split_generators).parameters:
        split_generators_kwargs["pipeline"] = prepare_split_kwargs["pipeline"]
    split_generators_kwargs.update(super()._make_split_generators_kwargs(prepare_split_kwargs))
    return split_generators_kwargs

In the latest main(in my fork and og repo's main):

def _make_split_generators_kwargs(self, prepare_split_kwargs):
    """Get kwargs for `self._split_generators()` from `prepare_split_kwargs`."""
    splits = prepare_split_kwargs.pop("splits", None)
    if self._supports_partial_generation():
        return {"splits": splits}
    return {}

It enables passing splits into _split_generators() only for builders that support it(if i am not wrong..). So ignored Beam logic for now!