[FRONTEND] Make admin availability display the available dates

[bcho892]

Is your feature request related to a problem? Please describe.

Right now on the availability page it displays "open" for available dates (shown below)

You will have to edit client\src\components\composite\Admin\AdminAvailabilityView\AdminAvailabilityView.tsx

Instead, we want it to actually show the availabilities:

It will just involve doing something similar to #288

You should also replace the manual timestamp conversions with the function timestampToDate in client\src\components\utils\Utils.tsx

BEFORE MERGING

• [ ] Storybooks created where possible
• [ ] Tested with nock if data fetching
• [ ] Tests written for critical interactions
• [ ] PR Reviewed (For non-trivial changes)
• [ ] Changes tested after rebasing on master or merging in master (hint: git fetch origin master:master, then git rebase master or git merge master)
• [ ] All required PR checks passing