(REF) Remove _tagElement dynamic property

[braders]

Overview

The $_tagElement property was a bit odd. Look at how it was used:

foreach ($this->_tags as $tagID => $tagName) {
  $this->_tagElement = &$this->addElement('checkbox', "tag[$tagID]", NULL, $tagName);
}

Issues with this code:

1. The _tagElement is being re-written on each iteration of the loop. So $this->_tagElement will point to the last element of the loop. I can't see how that is useful for anyone? If it was $this->_tagElement[] = ... then maybe; but it's not
2. The &$this shows how old this code is. If I understand correctly this was required in PHP4 when objects were not passed as reference by default. I checked the hisory of one file and the property was added when the functionality was first developed, not as part of a later ticket.
3. $this->_tagElement is a dynamic property, which is deprecated in PHP 8.2.
4. _tagElement is written, but never read or used in core.

We could add a @deprecated annotation to $_tagElement first, but based on the above I think it's unlikely third-parties are using _tagElement and I suspect it's safe to just remove.

CRM/Contact/Form/Search.php did specify $_tagElement explicitly, but as the task classes don't extend CRM_Contact_Form_Search that doesn't make any sense...

With this change no references to _tagElement remain in core.

[civibot]

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