Merge WPMangaReader and WPMangaStream

[AntsyLich]

Still need some work so draft

Checklist:

• [ ] Updated extVersionCode value in build.gradle for individual extensions
• [ ] Updated overrideVersionCode or baseVersionCode as needed for all multisrc extensions
• [ ] Referenced all related issues in the PR body (e.g. "Closes #xyz")
• [ ] Added the isNsfw = true flag in build.gradle when appropriate
• [ ] Have not changed source names
• [ ] Have explicitly kept the id if a source's name or language were changed
• [ ] Have tested the modifications by compiling and running the extension through Android Studio