Issue 900 refactor new cordova view with frame

[msmtamburro]

Platforms affected

Motivation and Context

Addressing the PR comment here warranted its own pull request: https://github.com/apache/cordova-ios/pull/1050#discussion_r552788845

Description

I've cleaned up newCordovaViewWithFrame in order to extract webViewEngine initialization with configuration, when provided and supported.

Testing

Checklist

• [x] 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