[Due for payment 2026-05-26] Decompose IOURequestStepConfirmation for Create Expense performance

[Julesssss]

Sub-issue of #81849, coming from here.

Comment related to this task.

Task

IOURequestStepConfirmation is ~1700 lines with 41 Onyx subscriptions handling 8 submission flows. 58% of those subscriptions are only accessed on confirm press, causing unnecessary re-renders throughout the Create Expense flow.

• Extract side-effect hooks into renderless components
• Move callback-only subscriptions behind refs
• Split into focused variant components per submission type

Initial PR here: #86865

Issue Owner

Current Issue Owner: @mallenexpensify

[Julesssss]

PR merged 🎉