feat: add HFB Pro components in Inserter

[HardeepAsrani]

Summary

This PR adds all the available Header/Footer elements to appear in the pro-upsell and search to for better discoverability of the elements.

Will affect visual aspect of the product

YES/NO

Screenshots

Test instructions

• Make sure the search works and you see all the elements from Pro.

Check before Pull Request is ready:

• I have written a test and included it in this PR
• I have run all tests and they pass
• The code passes when running the PHP CodeSniffer
• Code meets WordPress Coding Standards for PHP, HTML, CSS and JS
• Security and Sanitization requirements have been followed
• I have assigned a reviewer or two to review this PR (if you're not sure who to assign, we can do this step for you)

Closes #.

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🌍 i18n String Review Report

📊 Summary

Category	Count
➕ Added	2
➖ Removed	0
🔄 Changed	0
Total	2

➕ Added Strings (2) - Click to expand

String	Location	Words	Suggested Match
Copyright	neve/header-footer-grid/C...	1	Change Copyright
Widget Area	neve/header-footer-grid/C...	2	No close match
Total		3

[HardeepAsrani]

@vytisbulkevicius I've used similar strings, like "Divider element" instead of "Divider" and "Search Form" instead of "Advanced Search Form" to limit the string count to only 2. Let me know what you think.

[vytisbulkevicius]

@HardeepAsrani it looks good but I would also fill this place with 2 more Components:

We can add "Primary Menu" and "Button" (they exist as free as well but since we add more in PRO it's good to showcase them and don't create the feeling that all of them are listed when that space is not used, also we do this with "Search Form" already which appears both in Free and locked).

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🎉 This PR is included in version 4.2.0 🎉

The release is available on GitHub release

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