Improve user warnings and logic for remove_transformers and remove_transformers_by_sdtype

[amontanez24]

Problem Description

As a user, I want to be able to remove transformers from columns even if they are part of a multi_column transformer. The other columns should still go through that transformer.

Expected behavior

remove_transformers

• When removing a transformer for a column, if that column is assigned to a multi-column transformer, assign its transformer to None, but leave the other columns.

# before
>>> ht.get_config()
{
  'sdtypes': {
    'A': 'city',
    'B': 'state',
    'C': 'country'
  },
  'transformers': {
    ('A', 'B', 'C'): RandomLocationGenerator()
  }
}

# removing one of the columns in this transformer
>>> ht.remove_transformers(column_names=['A'])
>>> ht.get_config()
{
  'sdtypes': {
    'A': 'city',
    'B': 'state',
    'C': 'country'
  },
  'transformers': {
    'A': None,
    ('B', 'C'): RandomLocationGenerator()
  }
}

remove_transformers_by_sdtype

This works similarly to remove_transformers() but for all matching columns

# before
>>> ht.get_config()
{
  'sdtypes': {
    'A': 'city',
    'B': 'state',
    'C': 'country'
  },
  'transformers': {
    ('A', 'B', 'C'): RandomLocationGenerator()
  }
}
>>> ht.remove_transformers_by_sdtype(
      sdtype='city', transformer='AnonymizedFaker')
>>> ht.get_config()
{
  'sdtypes': {
    'A': 'city',
    'B': 'state',
    'C': 'country'
  },
  'transformers': {
    'A': None,
    ('B', 'C'): RandomLocationGenerator()
  }
}