dev/Core#785: Extend addField to support select2 widget

[monishdeb]

Overview

Currently, CiviCRM support select widget via Form::addField() but that doesn't allow us to use the features of select2 like rendering icon against each option. This PR extends addField() to support select2 widget along with select

Before

Suppose you want to add an icon only against smart group option(s) it was not possible earlier to simply use

$groupHierarchy = [
1 => [
   .. metdata..
  'name' => 'Smart Group'
   icon => 'fa-bulb-o'
  ],
..
];

$this->addField('group', array[
          'entity' => 'group_contact',
          'label' => ts('in'),
          'placeholder' => ts('- any group -'),
          'options' => $groupHierarchy,
          'type' => 'Select',
        ]);

won't work.

After

But this will:

$this->addField('group', array[
          'entity' => 'group_contact',
          'label' => ts('in'),
          'placeholder' => ts('- any group -'),
          'options' => $groupHierarchy,
          'type' => 'Select2',
        ]);

[civibot]

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[monishdeb]

Thanks @mattwire :)

[monishdeb]

Thanks @seamuslee001 for merging it :)