Fleet UI: Calendar settings iterations

[RachelElysia]

Issue

Iteration of #17444

Description

• Add JSON error handling to UI
• Add escape characters to format placeholder text correctly
• Several styling nits

Screenrecording

https://www.loom.com/share/e22095de4a7a44e69a155f11f08c1878?sid=1d1e0285-d96c-4281-9586-2ae742b10c65

Checklist for submitter

If some of the following don't apply, delete the relevant line.

• Manual QA for all new/changed functionality

[codecov]

Codecov Report

Attention: Patch coverage is 10.00000% with 9 lines in your changes are missing coverage. Please review.

Project coverage is 65.23%. Comparing base (268dd18) to head (53a7ab1).
Report is 3 commits behind head on 17230-calendar-feature.

Files	Patch %	Lines
...min/IntegrationsPage/cards/Calendars/Calendars.tsx	10.00%	9 Missing ⚠️

Additional details and impacted files

@@                    Coverage Diff                     @@
##           17230-calendar-feature   #17779      +/-   ##
==========================================================
- Coverage                   65.24%   65.23%   -0.01%     
==========================================================
  Files                        1202     1202              
  Lines                      109371   109380       +9     
  Branches                     2587     2590       +3     
==========================================================
+ Hits                        71358    71359       +1     
- Misses                      32598    32606       +8     
  Partials                     5415     5415              

Flag	Coverage Δ
frontend	51.48% <10.00%> (-0.05%)	⬇️

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[jacobshandling]

I think it's worth it to work within the current error typing paradigm using type predicates instead of updating the global typescript rule.

Also this color shouldn't be greyed, since it's not placeholder text but the actual value to copy:

fixed!

[jacobshandling]

Nice. This is probably something we can have as a utility type/typeguard for use across the UI.