Add PrettyBlocks FAQ selection block and allowlist template

[CySSoO]

Motivation

• Provide a PrettyBlocks block that lets editors pick registered FAQ entries via a repeater selector so selected FAQs can be displayed as an accordion using existing FAQ markup and schema.
• Ensure the new PrettyBlocks template file is recognized by the module by adding it to the module allowlist.

Description

• Register a new block everblock_faq_selection in src/Service/EverblockPrettyBlocks.php and expose a faq selector via the EverblockFaq collection for use in the block repeater.
• Add views/templates/hook/prettyblocks/prettyblock_faq_selection.tpl which resolves selected FAQ IDs, loads entries with EverblockFaq::getByIds, and includes the existing module:everblock/views/templates/hook/faq.tpl for rendering.
• Add the new template path to config/allowed_files.php so the template is included in the module allowlist.

Testing

• No automated tests were run for this change (not requested).

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Codex Task