refactor(auth): remove RelativeLayout usage

[thatfiredev]

See discussion in #1217

This is a Work-In-Progress:

Anonymous Auth

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Email Password

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Facebook

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Firebase UI

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Generic IDP

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Google

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Multi Factor Auth

I changed this one to give it a better look because the buttons were all squeezed in there.

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Passwordless

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Phone Auth

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[samtstern]

Approved with some small questions about changes to button groups.

[samtstern]

Is this the right change? We used to hide a group of buttons now you're just hiding one.

[thatfiredev]

Yes, the change is correct. That group was a LinearLayout containing only a single button, so I removed it and kept the button only.

quickstart-android/auth/app/src/main/res/layout/activity_passwordless.xml

Lines 110 to 130 in 368ff73

	<LinearLayout
	android:id="@+id/signedInButtons"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:layout_centerInParent="true"
	android:orientation="horizontal"
	android:paddingLeft="16dp"
	android:paddingRight="16dp"
	android:visibility="gone">
	<Button
	android:id="@+id/signOutButton"
	android:layout_marginStart="@dimen/button_horizontal_margin"
	android:layout_marginEnd="@dimen/button_horizontal_margin"
	android:layout_width="0dp"
	android:layout_height="wrap_content"
	android:layout_weight="1.0"
	android:text="@string/sign_out"
	android:theme="@style/ThemeOverlay.MyDarkButton" />
	</LinearLayout>

[samtstern]

Same here

[thatfiredev]

Addressed above, but I double checked:

quickstart-android/auth/app/src/main/res/layout/activity_phone_auth.xml

Lines 121 to 140 in 368ff73

	<LinearLayout
	android:id="@+id/signedInButtons"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:layout_centerInParent="true"
	android:orientation="horizontal"
	android:paddingLeft="16dp"
	android:paddingRight="16dp"
	android:visibility="gone"
	android:weightSum="1.0">
	<com.google.android.material.button.MaterialButton
	android:id="@+id/signOutButton"
	android:layout_width="0dp"
	android:layout_height="wrap_content"
	android:layout_weight="1.0"
	android:text="@string/sign_out"
	android:theme="@style/ThemeOverlay.MyDarkButton" />
	</LinearLayout>

[samtstern]

@rosariopfernandes makes sense, thank you! Also this PR taught me a lot about Guidelines and Groups in ConstraintLayout :-)

[thatfiredev]

@samtstern I'm glad :)

I noticed in your RTDB PR that we could've used a guideline (in activity_sign_in.xml) to center the textfields and replace their fixed width with match_constraint (0dp). I didn't comment on it because the previous Layout was also using fixed width, so I thought we could just leave as is. But if you want to try out Guidelines, I think that'd be a good place to do so ;)