simplify cooltools API - remove exotic `bad_bins` argument in favor of custom cooler weights

[sergpolly]

e.g. bad_bins here:

cooltools/cooltools/api/expected.py

Line 543 in ac36a82

bad_bins=None,

and in many other functions.

we introduced this additional level of complexity into cooltools API, that isn't widely used - and is somewhat redundant (same is achievable by registering custom weight column in cooler )

Should we remove it from cooltools ?