Stop reflecting request.GET into pagination links

[chosak]

The pagination module (molecules/pagination.html) currently generates its previous/next links by taking request.GET and appending "page" to the query string. This behavior carries over not just valid query string parameters (like "q", "topics", etc.) but any invalid ones that the user might append. For example, visiting a page like /about-us/newsrooom/ with query string ?dosomething=evil would generate pagination links like ?dosomething=evil&page=2.

This issue is covered in internal cfgov#4525.

This change refactors the pagination module so that it takes an explicit set of "pagination_params" that are used to generate links. Each caller using the pagination module must provide a base set of parameters.

This touches every place (9) that pagination is used on cf.gov. For local testing with a current site dump, try the use cases below. Note that although the URLs include invalid parameters, those are not carried over to the pagination links.

1. Filterable list results, for example http://localhost:8000/archive/blog/?page=3&categories=at-the-cfpb&invalid=badparam.
2. iRegs search results, for example http://localhost:8000/rules-policy/regulations/search-regulations/results/?page=2&q=test&regs=1002&order=relevance&results=25&invalid=badparam.
3. TDP activity search, for example http://localhost:8000/consumer-tools/educator-tools/youth-financial-education/teach/activities/?page=2&grade_level=4&invalid=badparam.
4. Sitewide search, for example http://localhost:8000/search/?page=2&q=mortgage&invalid=badparam.
5. Credit card ageements search, for example http://localhost:8000/credit-cards/agreements/issuer/synchrony-financial/?page=2&invalid=badparam.
6. Ask CFPB portal page, for example http://localhost:8000/consumer-tools/credit-reports-and-scores/answers/basics/?page=2&invalid=badparam.
7. Ask CFPB search result, for example http://localhost:8000/ask-cfpb/search/?page=2&q=mortgage&invalid=badparam.
8. Ask CFPB tag browsing, for example http://localhost:8000/ask-cfpb/search-by-tag/interest/?page=2&invalid=badparam.
9. Prepaid agreements search, for example http://localhost:8000/data-research/prepaid-accounts/search-agreements/?page=2&q=visa&search_field=all&invalid=badparam.

[wpears]

Works like a dream. Thanks for finally fixing this in a way that's not just dependent on escaping.