Fix undesired animation

[waliid]

Description

This PR allows us to fix an undesired animation on the metadata view.

Changes made

• Renames some computed variables.
• Uses same logic for opacities.
• Hides bottom buttons when the UI should be hidden.

Checklist

• APIs have been properly documented (if relevant).
• The documentation has been updated (if relevant).
• New unit tests have been written (if relevant).
• The demo has been updated (if relevant).

[defagos]

Two other remarks while I was looking at the code (not related to your changes):

• .linear(duration: 0.2) should just be .defaultLinear.
• The Self in static let defaultLinear = Self.linear(duration: 0.2) can be removed.

Would you mind doing these changes and commit them? Thanks in advance!