Fix sort params in issues page refactor

What does this MR do?

This MR fixes the sort parameters in the issues page refactor (#322755 (closed)), which is behind the vue_issues_list feature flag defaulted to off.

On the existing Haml page, the page reloads when a new sort option is chosen. In the Vue refactor, when a new sort option is chosen the list is updated via AJAX and the URL parameters are programmatically updated so that the page can be bookmarked like before.

In the Vue refactor, the URL parameters were updated to order_by=created_at&sort=desc when sorting but in production it's actually sort=created_date. This was identified when running the feature specs with the vue_issues_list feature flag on. Also, the Priority, Label priority, Manual, and Blocking sort options only have one sort order on production, so these discrepancies were updated in the Vue refactor.

Changes to feature tests were made so that when the feature flag is removed, the specs for sorting will still pass.

Screenshots (strongly suggested)

No visual changes

Does this MR meet the acceptance criteria?

Conformity

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• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
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Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

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• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
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Related to #322755 (closed)