Bug - dark theme follow ups

[mcoker]

From #5535

• Is it possible to swap the brand image in examples where we are looking at the black on white PatternFly brand placeholder? I'm guessing that occurs because we have black text on a transparent background. See Brand and Card examples specifically.
• I'm noticing that outlined label borders have a weird pixelation in dark theme.
• I see that the background of the User menu changes when I switch to dark theme. Is that what we expect or want?
• There's a contrast failure on the read-only code editor.
• File upload drag over states fail contrast - should the background be a darker gray?
• Selectable cards

[mcarrano]

There are also issues with read-only and disabled states for Form control components. See

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• Forms (text area, text input)