Fix #7823: Select Account not always showing checkmark

[StephenHeaps]

Summary of Changes

• Bug in comparison to determine if an account is selected. Object instance was being compared instead of the account's id.

This pull request fixes #7823

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 Wallet Panel and tap the blockie for the selected account
2. In the Select Account modal, verify the checkmark is shown as expected.
3. Select a different account, then re-open Select Account and verify the checkmark is shown as expected.
4. Add a new account, verify checkmark is shown as expected

Screenshots:

account.select.checkmark.fixed.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).