editor: Add support for customizable soft wrap indentation

[arusahni]

Objective

• Soft wrapped lines currently inherit the indentation of their first line. This can be challenging for those coming from different editors, or with different expectations.
• Allow users to customize the soft wrap behavior to wrap with extra indent, or no indent at all.
• Fixes Extra indent for soft-wrapped lines #18687

Solution

• Introduce 3 soft-wrap indent configuration values (in addition to the default of same): none, extra_one, and extra_two (where they are multiples of the indent column width).
• Plumb indent configuration through to the various gpui and editor components that are concerned with wrapping.
• Update code action icon placement to accommodate none-level wrap indentation (preceded by a refactor of the function used to calculate its display row).
• Fixed an existing bug in WrapSnapshot::soft_wrap_indent where querying a 0-indent wrap returned None instead of Some(0)

Testing

• Added tests to wrap_map.rs for all indentation levels.
• Updated the random wrap tests to include indent setting combinations.
• Added tests for code action icon placement.
• Validated locally by toggling between the various settings and observing how the wrap behaved.

Self-Review Checklist:

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments
• The content adheres to Zed's UI standards (UX/UI and icon guidelines)
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable

Showcase

Screenshots below! Changes are grouped by commit to ease review.

Click to view showcase

same indent (current Zed behavior)

none indent

extra_one indent

extra_two indent

the setting

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Release Notes:

• Added a soft_wrap_indent setting ("none", "same", "extra_one", "extra_two") to configure indentation for soft-wrapped continuation lines.
• Fixed soft-wrap continuation line indentation calculation for unindented lines starting at column 0.

[SomeoneToIgnore]

Thank you for the PR: seems that all checks fail due to the code not being able to compile: will close it for now as we'd want something a bit more finished and polished on the topic.

[arusahni]

@SomeoneToIgnore ugh, that's an embarrassing oversight on my part - I missed some tests when changing a function signature. I'm sorry for wasting some of your cycles.

I have pushed this out (fixed) as a different PR in #63468