Fix #6460: Buy/Send/Swap autodismiss from asset detail screen

[nuo-xu]

Summary of Changes

When Buy/Send/Swap is current presented, WalletPromptView will not trigger any top view controller to be dismissed.

This pull request fixes #6460

Submitter Checklist:

• Unit Tests are updated to cover new or changed functionality
• User-facing strings use NSLocalizableString()
• New or updated UI has been tested across:
  • Light & dark mode
  • Different size classes (iPhone, landscape, iPad)
  • Different dynamic type sizes

Test Plan:

1. open brave wallet
2. go to any asset detail screen that has buy/send/swap option
3. try to click those option quickly before asset detail is loaded
4. observe buy/send/swap will not be dismissed after details screen is loaded at the back
5. you can also try to change selected account or selected network in buy/send/swap
6. observe buy/send/swap screen will be not be dismissed after you changed selected account/network

Screenshots:

Simulator.Screen.Recording.-.iPhone.SE.3rd.generation.-.2022-11-23.at.09.58.28.mp4

Reviewer Checklist:

• Issues include necessary QA labels:
  • QA/(Yes|No)
  • bug / enhancement
• Necessary security reviews have taken place.
• Adequate unit test coverage exists to prevent regressions.
• Adequate test plan exists for QA to validate (if applicable).
• Issue and pull request is assigned to a milestone (should happen at merge time).