Fix all bugs in Login Example screen

[HariAcidReign]

The problem: TLDR: Both screens in Login Example are now part of the same screen. KeyboardAvoidingView treats them as 2 separate components and causes bugs in Portrait and especially Landscape mode. This PR solves that issue.

When form input is clicked in both Screen2 and 3, the entire view goes up and gets permanently hidden. The reason behind this bug is the KeyboardAvoidingView (KAV) which pushes the elements up upon clicking a form input.

Now, this library was required when both the Screen2 and 3 were in different sections (which can be accessed by sliding right), but now both the Screens are on the same page to avoid confusion and enable Landscape mode. This makes the KAV library redundant, as the forms in both Screens can just be scrolled both in Portrait and Landscape modes.

To replicate the bug: In both Portrait and Landscape modes, try to fill values in Screen2 and 3 on LoginExample page. Not using KAV gives a much better UI experience.

Open to suggestions, and willing to implement them 🙌🏻

[HariAcidReign]

Another Bug Fix in this PR: Incorrectly displaying Success Alert message in Screen3 even if input validation fails. I'm fixing that bug here itself to avoid merge conflicts.

[HariAcidReign]

What this PR achieves:

• Screens in Login Example don't hide out of sight on clicking a form input
• Alert in Screen3 is now in accordance with the result of input validation of the Login/Signup form
• Need Help? button now shows an alert on click, which can be modified by end-user/ dev to their app needs

All the bugs in the Login Example screen have been squashed. 🙌🏻