Add apply_keep_to_only_items_in_filter option to filter_arrays_by_meta

[jkgoodrich]

I have a case where I want to filter my meta_freq to

[{'group': 'adj'}, {'group': 'raw'}, {'gen_anc': 'afr', 'group': 'adj'}, {'gen_anc': 'amr', 'group': 'adj'}, {'gen_anc': 'asj', 'group': 'adj'}, {'gen_anc': 'eas', 'group': 'adj'}, {'gen_anc': 'fin', 'group': 'adj'}, {'gen_anc': 'mid', 'group': 'adj'}, {'gen_anc': 'nfe', 'group': 'adj'}, {'gen_anc': 'remaining', 'group': 'adj'}, {'gen_anc': 'sas', 'group': 'adj'}, {'group': 'adj', 'sex': 'XX'}, {'group': 'adj', 'sex': 'XY'}, {'gen_anc': 'afr', 'group': 'adj', 'sex': 'XX'}, {'gen_anc': 'afr', 'group': 'adj', 'sex': 'XY'}, {'gen_anc': 'amr', 'group': 'adj', 'sex': 'XX'}, {'gen_anc': 'amr', 'group': 'adj', 'sex': 'XY'}, {'gen_anc': 'asj', 'group': 'adj', 'sex': 'XX'}, {'gen_anc': 'asj', 'group': 'adj', 'sex': 'XY'}, {'gen_anc': 'eas', 'group': 'adj', 'sex': 'XX'}, {'gen_anc': 'eas', 'group': 'adj', 'sex': 'XY'}, {'gen_anc': 'fin', 'group': 'adj', 'sex': 'XX'}, {'gen_anc': 'fin', 'group': 'adj', 'sex': 'XY'}, {'gen_anc': 'mid', 'group': 'adj', 'sex': 'XX'}, {'gen_anc': 'mid', 'group': 'adj', 'sex': 'XY'}, {'gen_anc': 'nfe', 'group': 'adj', 'sex': 'XX'}, {'gen_anc': 'nfe', 'group': 'adj', 'sex': 'XY'}, {'gen_anc': 'remaining', 'group': 'adj', 'sex': 'XX'}, {'gen_anc': 'remaining', 'group': 'adj', 'sex': 'XY'}, {'gen_anc': 'sas', 'group': 'adj', 'sex': 'XX'}, {'gen_anc': 'sas', 'group': 'adj', 'sex': 'XY'}]

removing all downsamplings and subsets, but by indicating the groups I want to keep rather than those I want to remove.

    freq_meta, array_exprs = filter_arrays_by_meta(
        ht.freq_meta,
        {
            "freq": ht.freq,
            "freq_meta_sample_count": ht.index_globals().freq_meta_sample_count,
        },
        ["group", "gen_anc", "sex"],
        combine_operator="or",
        apply_keep_to_only_items_in_filter=True,
    )

I have no clue what to name this though, so feel free to suggest other names.

The `apply_keep_to_only_items_in_filter` parameter can be used to apply the `keep`
parameter to only the items specified in the `items_to_filter` parameter. For
example, by default, if:
    - `keep` is True
    - `combine_operator` is "and"
    - `items_to_filter` is ["sex", "downsampling"]
then all items in `meta_expr` with both "sex" and "downsampling" as keys will be
kept. However, if `apply_keep_to_only_items_in_filter` is True, then the items
in `meta_expr` will only be kept if "sex" and "downsampling" are the only keys in
the meta dict.

[mike-w-wilson]

This looks good -- a couple ideas on the arg naming

[mike-w-wilson]

LGTM!