feat: instant transaction support with confirmation render optimizations

[matthewwalsh0]

Description

Optimize the confirmation render path for instant transactions. Navigate to the confirmation screen before controller work completes, cache token icon state to prevent flicker during data hydration, and reduce unnecessary re-renders across the confirmation flow.

Depends on core PR for startTransaction support: MetaMask/core#8248

Changelog

CHANGELOG entry: Improved confirmation screen load performance for transactions

Related issues

Fixes:

Manual testing steps

1. Open dev options in confirmations and trigger an instant transaction
2. Confirmation screen should appear immediately without blank/loading state
3. Token icons should not flicker as transaction data hydrates
4. Standard (non-instant) transaction flow should be unaffected

Screenshots/Recordings

N/A

Pre-merge author checklist

• I've followed MetaMask Contributor Docs and MetaMask Mobile Coding Standards.
• I've completed the PR template to the best of my ability
• I've included tests if applicable
• I've documented my code using JSDoc format if applicable
• I've applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.