[NT-167] Update constraints for alert banner landscape support

[singhhari]

📲 What

The alert banner we present is currently constrained in such a way that, on landscape, the notch present on newer iPhone models is obstructing some of the view. The view controller that handles this alert banner is supported with a xib which requires some updates to the leading and trailing constraints.

🤔 Why

iOS allows developers to constraint views to a safe area, which was a useful way to avoid interactions with the extreme edges of the phone. It appears the implementation for our portrait support was fine but landscape had some minor issues.

🛠 How

Updated the xib file handling the alert banner to constraint leading and trailing to the safe area.

👀 See

[codecov]

Codecov Report

Merging #1359 (e5981ac) into master (77cca6c) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1359      +/-   ##
==========================================
- Coverage   86.05%   86.05%   -0.01%     
==========================================
  Files        1099     1099              
  Lines       97628    97628              
==========================================
- Hits        84012    84011       -1     
- Misses      13616    13617       +1     

Impacted Files	Coverage Δ
Library/Navigation.swift	76.89% <0.00%> (-0.37%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 77cca6c...e5981ac. Read the comment docs.