[Auth] Copied over CredentialsActivity from Simperium to customize login screen.

[notandyvee]

Fix

We have a requirement where during the new login flow, if the user decides to login with password we will hide the email field. In it's place we show some text indicating what the email is.

Doing this required some simperium changes. But it's a pain to get this to work. Instead I opted to copy over the activity and converted it into kotlin. I also removed SimpleNoteCredentialsActivity and just took the logic from there and added it to the NewCredentialsActivity.

The goal here is to move the business logic into a ViewModel and also extract the code out into a fragment. But to keep the changes to a minimum considering the kotlin conversion, I will save that work for later.

Test

• [ ] Select Login
• [ ] Enter your email and click "Log in with email"
• [ ] On the next screen select "Enter password".
• [ ] On this screen you should see some text at the top with the email to login with and a password field.
• [ ] Make sure logging in by password still works here.

Release

n/a

[dangermattic]

	3 Warnings
:warning:	strings.xml files should only be updated on release branches, when the translations are downloaded by our automation.
:warning:	This PR is larger than 300 lines of changes. Please consider splitting it into smaller PRs for easier and faster reviews.
:warning:	PR is not assigned to a milestone.

Generated by :no_entry_sign: Danger

[wpmobilebot]

📲 You can test the changes from this Pull Request in Simplenote Android by scanning the QR code below to install the corresponding build.

	App Name	Simplenote Android
	Build Type	Debug
	Commit	bdfc9b99ebde65128c07fbde33efbe7afa7878c9
	Direct Download	simplenote-android-prototype-build-pr1671-bdfc9b9-01914d95-4545-451a-b5b3-62f2f92323f2.apk

[notandyvee]

@danilo04 bumping you for a quick review when you get a chance.