[Jetpack] Show Jetpack plugin install prompt during Jetpack app login process

[staskus]

This is an issue to track tasks related to "Jetpack install prompt during Jetpack app login process feature".

Description

Ask self-hosted Jetpack app users if they'd like to install Jetpack during the login process.

Parent Branch

feature/19213-jetpack-install-prompt https://github.com/wordpress-mobile/WordPress-iOS/compare/feature/19213-jetpack-install-prompt?expand=1

Phase 1:  Prompt users to install Jetpack during the login process

• [x] Integrate previously started changes on the new branch: (feature/19213-jetpack-install-prompt)
• [x] Test previously created changes on different screen sizes and configurations
• [x] Show the prompt once per site
• [x] https://github.com/wordpress-mobile/WordPress-iOS/pull/19225
• [x] https://github.com/wordpress-mobile/WordPress-iOS/pull/19234
• [x] https://github.com/wordpress-mobile/WordPress-iOS/pull/19240
• [x] Feature flag https://github.com/wordpress-mobile/WordPress-iOS/pull/19240 last commit
• [x] Accessibility https://github.com/wordpress-mobile/WordPress-iOS/pull/19250
• [x] RTL Support https://github.com/wordpress-mobile/WordPress-iOS/pull/19250
• [x] Write UI tests and update the current ones (testAddSelfHostedSiteAfterWPcomLogin, testSelfHostedLoginLogout, testWPcomLoginLogout are failing)
• [x] Consider unifying prompt visibility logic for login and stats/notifications
• [x] Issue on iPad, since Stats are already opened, we need to refresh Stats when installation is complete, if we don't, Stats continue showing "Install" https://github.com/wordpress-mobile/WordPress-iOS/pull/19269
• [x] https://github.com/wordpress-mobile/WordPress-iOS/pull/19302
• [x] https://github.com/wordpress-mobile/WordPress-iOS/pull/19330
• [x] Consider Release Notes