enable pileups in asymmetric coolers

[golobor]

[sergpolly]

potential "forced" implementation from @Phlya @agalitsyna branch:

    ### Draft "force" implementation:
    # if not force:
    #     if feature_type=='bed':
    #         if not bioframe.is_bedframe(features_df[['chrom', 'start', 'end']]):
    #             raise ValueError("features_df is not a valid bedframe, use force=True if you still want to use it.")
    #     elif feature_type=='bedpe':
    #         if not bioframe.is_bedframe(features_df.rename({'chrom1': 'chrom', 'start1':'start', 'end1':'end'}, axis=1)[['chrom', 'start', 'end']]) or \
    #             not bioframe.is_bedframe(features_df.rename({'chrom2': 'chrom', 'start2':'start', 'end2':'end'}, axis=1)[['chrom', 'start', 'end']]):
    #                 raise ValueError("features_df first or second coordinates does not represent a valid bedframe, use force=True if you still want to use it.")

    ### Mask out of bounds features?
    # features_df["region"] = np.where(
    #     np.logical_and(
    #         features_df["end"]
    #         <= features_df["region"].replace(
    #             view_df[["name", "end"]].set_index("name")["end"]
    #         ),
    #         features_df["start"] >= 0,
    #     ),
    #     features_df["region"],
    #     None,
    # )