Add version utilities

[ernilambar]

Add version utilities:

• Add get_wordpress_stable_version() similar to that helper method in Plugin_Readme_Check class
• New methods to fetch version informations
  • get_wordpress_latest_version()
• Added Version_Utils_Tests unit test class

[github-actions]

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Co-authored-by: ernilambar <rabmalin@git.wordpress.org>
Co-authored-by: davidperezgar <davidperez@git.wordpress.org>
Co-authored-by: mukeshpanchal27 <mukesh27@git.wordpress.org>
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[ernilambar]

On second thought, this could be alternative naming convention:

• get_wordpress_stable_version()
• get_wordpress_latest_version()
• get_php_required_version()
• get_php_recommended_version()
• get_mysql_required_version()

[ernilambar]

PR updated with new naming pattern.

Also added get_wordpress_relative_major_version() method to find relative WP major version.