[#396] Frontend for Privacy Request denial flow

[TheAndrewJackson]

Purpose

Update the FE to use the denial reason audit logs that were added in #397

Changes

• Update the Deny Privacy Request button to pull up a modal that allows a user to enter a denial reason

Checklist

• Applicable documentation updated (guides, quickstart, postman collections, tutorial, fidesdemo, database diagram.
• If docs updated (select one):
  • documentation complete, or draft/outline provided (tag docs-team to complete/review on this branch)
  • documentation issue created (tag docs-team to complete issue separately)
• Good unit test/integration test coverage
• This PR contains a DB migration. If checked, the reviewer should confirm with the author that the down_revision correctly references the previous migration before merging
• The Run Unsafe PR Checks label has been applied, and checks have passed, if this PR touches any external services

Ticket

Fixes #396

[LKCSmith]

I wasn't able to spin-up any mock subject (privacy?) requests locally to test this out, so this is purely a code review.