Bug 307823 – Cleanup display property style representation

• Status: RESOLVED
• Resolution: FIXED
• Component: CSS

[Sam Weinig]

Cleanup display property style representation.

- Moved enum from RenderStyleConstants.h to StyleDisplay.h and into the Style namespace.
- Moved predicates from RenderStyle to StyleDisplay.h and into the Style namespace.

- Renames enum values to the non-shortened names to make outside/inside structure more clear.
- Renames `equivalentBlockDisplay()`/`equivalentInlineDisplay()` to `blockify()`/`inlinify()`, matching their spec names and related predicates (like the existing `shouldInlinifyForRuby()`). 
- Renames `setEffectiveDisplay` to `setDisplayMaintainingOriginalDisplay` to make it clear what it is doing. Also removes the `effectiveDisplay` terminology entirely, renaming the member variable from `effectiveDisplay` to `display`.

- Add CSSValueConversion implementation. This will be needed for properly implementing `block ruby` serialization in a forthcoming change.
- Add ValueRepresentation implementation. This allows us to remove the logging and toCSSValueID implementations, and will also be needed for properly implementing `block ruby` serialization in a forthcoming change. 
- Add Blending implementation to remove another use of custom animation wrappers/functions.

[Sam Weinig]

Pull request: https://github.com/WebKit/WebKit/pull/58649

[EWS]

Committed 307580@main (70c23162b81c): <https://commits.webkit.org/307580@main>

Reviewed commits have been landed. Closing PR #58649 and removing active labels.

[Radar WebKit Bug Importer]

<rdar://problem/170395254>