UL&S: Implements re-authentication flow tracking.

[diegoreymendez]

WPAuth PR: wordpress-mobile/WordPressAuthenticator-iOS#489

Fixes an issue with tracking during re-authentication.
Implements the re-authentication flow tracking.

Testing:

Test 1:

1. Log in to a WP.com account
2. Using the web, disconnect WPiOS. (https://wordpress.com/me/security/connected-applications)
3. Do something in WPiOS that would trigger a network request.
4. Once the password screen is up check.

🔵 Tracked: unified_login_step <flow: login_password, source: reauthentication, step: start>

5. Tap on Help and verify:

🔵 Tracked: unified_login_interaction <click: show_help, flow: login_password, source: reauthentication, step: start>
🔵 Tracked: unified_login_step <flow: login_password, source: reauthentication, step: help>

6. Tap “Close” and verify:

🔵 Tracked: unified_login_interaction <click: dismiss, flow: login_password, source: reauthentication, step: help>

7. Enter the correct password, tap “Continue” and verify:

🔵 Tracked: unified_login_interaction <click: submit, flow: login_password, source: reauthentication, step: start>
🔵 Tracked: unified_login_step <flow: login_password, source: reauthentication, step: success>

PR submission checklist:

• I have considered adding unit tests where possible.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[peril-wordpress-mobile]

You can trigger an installable build for these changes by visiting CircleCI here.

[peril-wordpress-mobile]

You can trigger optional UI/connected tests for these changes by visiting CircleCI here.

[mindgraffiti]

✅ UI tested
✅ Events reported

🔵 Tracked: unified_login_step <flow: login_password, source: reauthentication, step: start>
🔵 Tracked: unified_login_interaction <click: show_help, flow: login_password, source: reauthentication, step: start>
🔵 Tracked: unified_login_step <flow: login_password, source: reauthentication, step: help>
🔵 Tracked: support_opened <>
🔵 Tracked: unified_login_interaction <click: dismiss, flow: login_password, source: reauthentication, step: help>
🔵 Tracked: unified_login_interaction <click: submit, flow: login_password, source: reauthentication, step: start>
🔵 Tracked: unified_login_step <flow: login_password, source: reauthentication, step: 2fa>
🔵 Tracked: unified_login_step <flow: login_password, source: reauthentication, step: success>

[diegoreymendez]

Thanks for the reviews @mindgraffiti !