Reader: Add new ReaderPostHeaderView

[kean]

This is first part of CMM-1999: Reader: Adaptive Post Details Page, which adds the new ReaderPostHeaderView to the WordPressReader module. It is implemented in UIKit because the rest of the screen is, and it requires manual frame manipulations: when the header resizes, it needs to update the container (scroll view) – it required too many extra steps with SwiftUI judging by the original implementation.

[dangermattic]

	1 Warning
⚠️	This PR is larger than 500 lines of changes. Please consider splitting it into smaller PRs for easier and faster reviews.

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[sonarqubecloud]

Quality Gate passed

Issues
14 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[wpmobilebot]

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

	App Name	WordPress
	Configuration	Release-Alpha
	Build Number	31838
	Version	PR #25463
	Bundle ID	org.wordpress.alpha
	Commit	e64a372
	Installation URL	154ia2rplq7c8

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

[wpmobilebot]

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

	App Name	Jetpack
	Configuration	Release-Alpha
	Build Number	31838
	Version	PR #25463
	Bundle ID	com.jetpack.alpha
	Commit	e64a372
	Installation URL	180rblp835gh0

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