FI-3318: Fix erroneous submit disabling for checkbox inputs

[AlyssaWang]

Summary

This bug was caused by some checkbox inputs getting improperly processed as JSON strings when they were actually arrays of strings. Adding a case to handle this particular typing prevents the error. This PR also refactors some of the InputModal logic to simplify the component logic and provide more consistent reactive handling of required inputs.

Testing Guidance

To reproduce: try to run Demo Group 1 in the Demonstration Suite; the Submit button should be disabled even though all required inputs have values.

After these changes, this should no longer occur -- all inputs should behave according to required input status. Also test JSON and YAML inputs to ensure those features still work as expected.

[codecov]

Codecov Report

Attention: Patch coverage is 37.12575% with 105 lines in your changes missing coverage. Please review.

Project coverage is 84.06%. Comparing base (1b13c9b) to head (73f1e38).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
client/src/components/InputsModal/InputHelpers.ts	29.32%	94 Missing ⚠️
client/src/components/InputsModal/InputsModal.tsx	66.66%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #548      +/-   ##
==========================================
- Coverage   84.08%   84.06%   -0.03%     
==========================================
  Files         261      262       +1     
  Lines       11392    11409      +17     
  Branches     1252     1254       +2     
==========================================
+ Hits         9579     9591      +12     
- Misses       1803     1808       +5     
  Partials       10       10              

Flag	Coverage Δ
backend	92.18% <ø> (ø)
frontend	79.33% <37.12%> (-0.03%)	⬇️

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