Additional operator for update_by requested

[lbooker42]

To support production use cases, we need the following operators (also found in #4424):

• median
• percentile
• var
• cor
• count_neg, count_pos
• cum_std

But also needed are the following (supported by pandas / Polars):

• last
• rank
• pct_change

[chipkent]

Other count operations like count_null, count_nan, etc. would be useful.

[chipkent]

As we have done in other cases, null values should be ignored, and NaN values are included -- typically resulting in poisoning.

[chipkent]

I looked through Pandas docs and found a few more operations that we should really support:

• kurt / kurtosis
• skew