NestedFrame constructor to pack series with hierarchical names

[hombit]

Feature request

It would be cool to allow users provide "layer.col" list-array series as input to NestedFrame so we automatically pack them.

nested_frame = NestedFrame(
    {
        {"id": [1,2,3]},
        {"lc.time": [0.1, 0.2], [0.1, 0.3], [0.2, 0.3, 0.4]},
        {"lc.counts": [100, 200], [55, 75], [33, 100, 155]},
    }
)

We can use it in reduce to allow a simple interface of generating new nested columns from it.

def apply_reference(ref_mag: float, ref_magerr: float, diff_mag: np.ndarray, diff_magerr: np.ndarray):
    mag = ref_mag + diff_mag
    magerr = np.hypot(ref_magerr, diff_magerr)
    return {"corrected_lc.mag": mag, "corrected_lc.magerr": magerr}

corrected_mag_df = nested_frame.reduce(apply_reference, "ref_mag", "ref_magerr", "lc.mag", "lc.magerr")
nested_frame = nested_frame.join(corrected_mag_df)
# Now nested_frame has "corrected_lc" column

Before submitting
Please check the following:

• I have described the purpose of the suggested change, specifying what I need the enhancement to accomplish, i.e. what problem it solves.
• I have included any relevant links, screenshots, environment information, and data relevant to implementing the requested feature, as well as pseudocode for how I want to access the new functionality.
• If I have ideas for how the new feature could be implemented, I have provided explanations and/or pseudocode and/or task lists for the steps.