Configurations for the new color/style used in metadata line and warning for the scrollable list view

Start by reading the discussion linked from the issue and the six existing comments to understand the unresolved configuration options for the metadata line and scrollable list warning. No files or tests are named, and the issue is complete only once the project has an agreed configuration design and corresponding implementation scope.

Prerequisites

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Description of the new feature/enhancement

This issue is to follow up on https://github.com/PowerShell/PSReadLine/pull/3583#discussion_r1109181920, the discussion about what to make configurable about the new color and styles used in the metadata line and warning for the scrollable list view.

About the new colors and styles, there are a few of them:

• un-highlighted texts in the metadata line
  • currently, the un-highlighted text uses the default inline view color/style -- this is fixed as of today.
• highlighted text in the metadata line
  • currently, the highlighted text uses the ListPredictionColor plus italics -- so, it partially configurable.
• warning message
  • currently, the warning message uses the ListPredictionColor plus italics.

I'm not sure about what to expose for configuration yet. It doesn't seem needed to expose them all in my opinion. The following are my thoughts at the moment:

1. always apply italics to the text rendered in the metadata line, and use the ListPredictionColor as the user-configurable highlighting color/style.
2. maybe expose configuration for un-highlighted text color/style, but I'm not super sure if it's really needed.
3. warning message will be uncommon for users to see because it will happen usually only when the terminal height is very small (<5). So, exposing a configuration for it seems overkill to me.

I don't have a clear idea what/how to make configurable about the new color/styles at the moment, so I prefer to wait and collect some feedback about this, which hopefully will give us a clearer idea.