[ext.pages] Fixes and enhancements for PageGroup handling

[krittick]

Summary

This PR does the following:

1. Fixes an issue where PageGroup objects were not respecting their default_button_row parameter due to a missing parameter in PaginatorMenu's callback to Paginator.update.
2. Fixes an issue where Paginator.update did not allow updating the pages parameter with a new list of PageGroup objects
3. Fixes other missing parameters in PaginatorMenu's callback to Paginator.update (timeout, trigger_on_display)
4. Adds support for specifying a default PageGroup object to show when the paginator is sent (controlled by a new default parameter on the PageGroup object)

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• If type: ignore comments were used, a comment is also left explaining why
• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, typehinting, examples, ...)