[Notification Refresh] Likes and follows notifications header redesign

[justtwago]

Fixes https://github.com/Automattic/wordpress-mobile/issues/16

This PR contains only the brand-new header UI and UX.

Post like	Comment like	Followers

To test:

• [ ] Login to the account that contains likes for posts and comments, and also followers.
• [ ] Navigate to the Notifications screen
• [ ] Find notifications for comment likes, post likes and a new follower
• [ ] The header's UI is the same as on the designs: the original content panel and navigation arrows are brand-new
• [ ] Click on the header to navigate to the like content or the followed blog as usual

Regression Notes

1. Potential unintended areas of impact Header navigation buttons and the original content panel actions.

2. What I did to test those areas of impact (or what existing automated tests I relied on) Manual tests.

3. What automated tests I added (or what prevented me from doing so) There have been no tests since the legacy code was changed only.

PR submission checklist:

• [x] I have completed the Regression Notes.
• [x] I have considered adding unit tests for my changes.
• [x] I have considered adding accessibility improvements for my changes.
• [x] I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

Testing checklist:

• [ ] WordPress.com sites and self-hosted Jetpack sites.
• [ ] Portrait and landscape orientations.
• [ ] Light and dark modes.
• [ ] Fonts: Larger, smaller and bold text.
• [ ] High contrast.
• [ ] VoiceOver.
• [ ] Languages with large words or with letters/accents not frequently used in English.
• [ ] Right-to-left languages. (Even if translation isn’t complete, formatting should still respect the right-to-left layout)
• [ ] iPhone and iPad.
• [ ] Multi-tasking: Split view and Slide over. (iPad)

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress Alpha by scanning the QR code below to install the corresponding build.

	App Name	WordPress Alpha
	Configuration	Release-Alpha
	Build Number	pr23107-eab1dc4
	Version	24.8
	Bundle ID	org.wordpress.alpha
	Commit	eab1dc4bb1aa6e4ed98f53948aeafc37e2a2489d
	App Center Build	WPiOS - One-Offs #9778

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack Alpha by scanning the QR code below to install the corresponding build.

	App Name	Jetpack Alpha
	Configuration	Release-Alpha
	Build Number	pr23107-eab1dc4
	Version	24.8
	Bundle ID	com.jetpack.alpha
	Commit	eab1dc4bb1aa6e4ed98f53948aeafc37e2a2489d
	App Center Build	jetpack-installable-builds #8824

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.