[6.x] Perhaps renaming "Theme" to "Color Mode" in code fieldtype (and add "System" as an option)

[helloDanuk]

Bug description

1. Perhaps renaming «Theme» in code fieldtype too

With the renaming in #13298 and while working on translations, I wondered whether the code fieldtype options for the theme are only light and dark?

Unless other theme options follow in the future, it would perhaps make sense to rename "Theme" to "Color Mode" at this point too? And the instruction text to: "Choose your preferred color mode."

Current instructions text

Might fit better?

2. Add "System" to options

If the options are referred to color modes, adding "System" to the options, would complete the list.

How to reproduce

Add a code fieldtype in the blueprint editor.

Logs

Environment

6.0.0-alpha.18

Installation

Fresh statamic/statamic site via CLI

Additional details

No response