[sitecore-jss-nextjs] Preserve basePath when doing redirects in redirects-middleware

[yavorsk]

• This PR follows the Contribution Guide
• Changelog updated
• Upgrade guide entry added

Description / Motivation

When basePath is configured in NextJs config make sure that it is preserved when doing redirects in redirects-middleware.
Example:

• basePath is configured in next.config: basePath: '/base-path',
• we have the following redirect map configured in Sitecore AI: /old-page -> /new-page
• Navigating 'https://my-site.com/base-path/old-page' should redirect to 'https://my-site.com/base-path/new-page'

Testing Details

• Unit Test Added
• Manual Test/Other (Please elaborate) - all redirects with configured NextJs basePath should work properly; test with both client side and server side navigation

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)