doc(ios): various platform guide updates for 8.0.0 release

[erisu]

Motivation and Context

Update platform guide docs for 8.0.0 release

Description

• Fixed nodejs requirement
• Updated screenshots
• Removed platform centered workflow as the steps no longer work
• Corrected how to open the app in Xcode with recent project name changes.

Testing

Built site locally

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change
• Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary