Issue #3208766: Add UUID to sections

Tasks:

• Add a UUID property to the Section class.
• Determine whether we will also need a weight property. It seems like the answer is yes for the purpose of this PR.
• Update appropriate calls to new Section() to include UUID when appropriate.
• Write an update hook to add UUID's to existing section instances.
• Update demo_umami and test profile config to include UUID's on sections in appropriate core.entity_view_display.* files.
• Update existing tests where needed.
• Figure out where to add assertions for new getUuid() and getWeight() methods in existing tests.
• Write an upgrade path test.