Hide username and password field for Connect apps

[OrangeAndGreen]

Summary

https://dimagi.atlassian.net/browse/CCCT-659

When a Connect app (i.e. learn or deliver app for an opportunity) is selected on the main login page, the username and password fields should be hidden so:

1. The user doesn't see their ConnectID in the username field (it can only confuse them)
2. The user can't override the grayed out password field and attempt to login with a password (Connect apps don't use passwords)

Release Note:
Username and password fields are hidden when logging into Connect apps.

cross-request: dimagi/commcare-core#1455

Feature Flag

Connect

Product Description

The username and password fields will now disappear when the user changes to a Connect app (or one is already seated at app startup). If the user changes to a traditional CommCare app, the fields will reappear.

PR Checklist

• If I think the PR is high risk, "High Risk" label is set
• I have confidence that this PR will not introduce a regression for the reasons below
• [ x ] Do we need to enhance manual QA test coverage ? If yes, "QA Note" label is set correctly
• [ x ] Does the PR introduce any major changes worth communicating ? If yes, "Release Note" label is set and a "Release Note" is specified in PR description.

Automated test coverage

No automated tests for Connect yet.

Safety story

Need to make sure the visibility of the username and password fields are correct in every scenario (traditional apps, ConnectID-managed apps, Connect apps).

Screenshots:
Traditional app login:

Connect login:

[shubham1g5]

Can we have the screenshot for login screen in PR for reference on how it looks like with these changes.

[OrangeAndGreen]

Added screenshots to the PR description