[MRF-8] PLU-520: New Approve-Reject component (frontend)

[pregnantboy]

Changes

This PR adds UI elements for approval/rejection flow in FormSG MRF steps and includes several improvements:

• Added an "If approved/If rejected" toggle UI component for FormSG MRF steps with approval fields
• Fixed a bug in createStep mutation to properly handle non-existent triggers/actions
• Refactored step metadata handling to improve code organization:
  • Moved FormSG-specific constants to a dedicated helper file
  • Improved step metadata detection with isApprovalStep flag
  • Consolidated step deletion logic into the useStepMetadata hook
• Removed the StepDisplayOverrides context in favor of useStepMetadata​

[pregnantboy]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• [MRF-8] PLU-520: New Approve-Reject component (frontend) #1284 : 2 dependent PRs (#1285 , #1349 ) 👈 (View in Graphite)
• [MRF-7] PLU-520: remove mrf actions steps if necessary #1275
• [MRF-6] PLU-520: testStep for mrf actions should test multiple steps #1269
• [MRF-5] PLU-520: refactor frontend to allow test step on mrf actions #1268
• [MRF-4] PLU-520: automatically create/delete/update mrf steps on check step #1267
• [MRF-3] PLU-520: introduce mrf action that cannot be added by user #1266
• [MRF-2] PLU-520: parse formsg workflow data + refactor #1265
• [MRF-1] PLU-520: allow mrf forms to be connected #1264
• mrf/trunk

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[linear]

PLU-520 MRF: Approvals

[kevinkim-ogp]

lgtm!

• isDeletable still works as intended
• Approve-Reject component is displayed correctly for approval steps
• Steps are created as intended