feat: move scroll to top to free version

[HardeepAsrani]

Summary

It's part of this PR: https://github.com/Codeinwp/neve-pro-addon/pull/3101

This PR moves Move to Scroll from Pro version to Free version. Few notes:

• It introduces new strings.
• It adds a migration for from the option to theme mod for enable/disable.

[PS; e2e were failing due to browesrs not being able to get downloaded, will trigger later]

Will affect visual aspect of the product

YES

Screenshots

Test instructions

• Test to make sure everything works properly, even in previously created websites.
• Test to make sure there are no errors or issues if this PR is used with an older version of Pro or if it the connected Pro version is used with an older version of Free.

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 https://github.com/Codeinwp/neve-pro-addon/issues/3083.

[pirate-bot]

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