[MOB-1114] Collect email when isEmailRequired sets to true

[aw-hector]

This pr:

• adds email field when isEmailRequired of AirwallexSession is set to true
• validates email format
• adds Requires Email in settings for testing convenience

[github-actions[bot]]

Unit Test Results

261 tests  +2   261 :heavy_check_mark: +2   1m 36s :stopwatch: -16s 100 suites +1       0 :zzz: ±0  100 files   +1       0 :x: ±0 

Results for commit 50f93a10. ± Comparison against base commit a4b7d05b.

:recycle: This comment has been updated with latest results.