updated how custom filters are implemented for the Table Report

[lisaleemcb]

Description

Previously, the custom_filters kwarg passed to the TableReport required a nested dict such as

CUSTOM_FILTERS = {'FILTER ID': {filter1: [0,1,2]}}.

Additionally, the only custom filter type that could be passed was a list of ints, indicating the indices of the desired columns.

My proposed change is to

a) streamline the user input such that only one dictionary is required, for example,
CUSTOM_FILTERS = {filter1: selector}

and

b) changed the required input to be a skrub Selector object.

Addresses #1969

TBC

• I have added tests that verify the bug fix
• I have added an entry to CHANGES.rst describing the fix
• My code follows the code style of this project
• I have checked my code and corrected any misspellings

How Has This Been Tested?

[rcap107]

Looks good to me, thanks a lot @lisaleemcb