[plg_content_pagebreak] Let users template override TOC

[ReLater]

See discussion here: #17670

Summary of Changes

• Added possibility to use a template override for TOC.
• Don't break B\C.
• BTW: Fix older bug: "Show All" never has active class even if active.

Testing Instructions

• Plugin "Content - Page Break". Make settings:

• Add some pagebreak markers to an article and open article in frontend.
• Inspect TOC (also source code).

• Apply patch.

• Inspect TOC (also source code).

• Expected: No changes.

• Create a template override for new file tmpl/toc.php.
  Example with Protostar:

• Check that the override works.

[dgrammatiko]

we need to make sure that all plugins are actually overridable! Great work here 👍

[Quy]

Change to per Joomla's Coding Standards.

<?php foreach ($list as $listItem) : ?>
        <?php $class = $listItem->liClass ? ' class="' . $listItem->liClass . '"' : ''; ?>

[Quy]

Remove tabs

[Quy]

I have tested this item ✅ successfully on 50c8e51

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[LivioCavallo]

I have tested this item ✅ successfully on 50c8e51

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/20202.}

[LivioCavallo]

Well done. Thanks. I tested it successfully. If all will be ok I'll close #17670

[Quy]

RTC

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