refactor(buttons): convert buttons in scans and credentials list views

[jenny-s51]

What's included

...
Converts PF3 buttons to PF4 buttons in list view of Scans and Credentials screens.

This includes the icons on the right of every list item, and the "Merge Reports" button on the Scans screen.

Notes

The changes in this PR are aligned with the code and feedback in #136

Example

...

Before

After

Updates issue/story

DISCOVERY-149
#134

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (dev@a104f02). Click here to learn what that means.
The diff coverage is n/a.

❗ Current head e17d910 differs from pull request most recent head b5c4c91. Consider uploading reports for the commit b5c4c91 to get more accurate results

@@          Coverage Diff           @@
##             dev     #142   +/-   ##
======================================
  Coverage       ?   75.97%           
======================================
  Files          ?      101           
  Lines          ?     3292           
  Branches       ?      920           
======================================
  Hits           ?     2501           
  Misses         ?      701           
  Partials       ?       90           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a104f02...b5c4c91. Read the comment docs.

[cdcabrera]

Double check with Ben on the button but otherwise, lgtm!

[bclarhk]

Yeah, not sure why the merge reports is/was a secondary button. It's the only real action on the page. Let's make it the primary button.

[jenny-s51]

Thank you for your reviews and feedback @cdcabrera @bclarhk !

I've switched the button to use the primary variant, and have uploaded a screenshot with the updated appearance of the "merge reports" button.