Instead of being updated on file rename, serialized contents of a Prefab only update when it is reserialized after an edit or other cause

How to reproduce:
1. Open or create a new project
2. From Hierarchy drag "Main Camera" onto Project window to create a new Prefab
3. In Project window rename the Prefab
3b. Select the menu item "File > Save project" (needed for pending changes to be saved to disk)
4. Open the renamed file in text editor
5. Search for `m_Name` property and inspect its value

Expected result: `m_Name` property in renamed Prefab matches its new name
Actual result: `m_Name` property contains old "Main Camera" value

Reproducible with: 2018.4.16f1, 2019.2.19f1, 2019.3.0f6, 2020.1.0a21
Not reproducible with: 2017.4.36f1 - Prefab file contents update after File->Save project is selected

Note, if not using "File > Save project" lots of Assets types will not have their name in the file updated. For example Materials. However, for Prefabs even doing this still doesn't update the name in the file, which is a Prefab specific bug. Added 3b to repro steps to clarify scope of bug.