Missing settings max_length or is_ascii for ListStringItem.

Problem/Motivation

I've the following definition,

     $fields['type'] = BaseFieldDefinition::create('list_string')
      ->setLabel(t('Type'))
      ->setDescription(t('The type of receiver'))
      ->setSettings([
        'max_length' => 16,
        'allowed_values' => [
          'email' => 'email',
          'mobile' => 'mobile',
        ],
      ]);

    $fields['receiver'] = BaseFieldDefinition::create('string')
      ->setLabel(t('Receiver'))
      ->setDescription(t('The email/phone to receive the OTP.'))
      ->setSettings([
        'max_length' => 192,
        'text_processing' => 0,
      ]);

    $fields['is_verified'] = BaseFieldDefinition::create('list_string')
      ->setLabel(t('Is Verified'))
      ->setDescription(t('Whether the OTP been verified or not'))
      ->setDefaultValue('pending')
      ->setSettings([
        'max_length' => 16,
        'allowed_values' => [
          'pending' => 'pending',
          'yes' => 'yes',
          'no' => 'no'
        ],
      ]);

Both BaseFieldDefinition::create('list_string') and BaseFieldDefinition::create('string') under the hood are using varchar(255) by default. While 'string' respects the 'max_length', the 'list_string' seems not taking that into account.

I'm hitting the InnoDB table limit while trying the index some columns. I guess the indexing would be successful if I could set optimal length for them.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

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