Editor: Standardize reduced motion handling using media queries

[himanshupathak95]

Part of: #68282

What?

Replace all instances of the reduce-motion mixin with standardized @media not (prefers-reduced-motion) media queries across the editor package components to improve code consistency and maintainability.

Testing Instructions

Test Document Bar and Tools:

• Open the editor
• Hover over the document bar buttons
• Click the inserter toggle (+ button)
• Verify smooth transitions with motion-enabled
• Verify instant changes with reduced motion enabled

Test Publish Panel:

• Click the publish/update button
• Observe the panel slide-in
• Verify smooth animation with motion-enabled
• Verify instant appearance with reduced motion enabled

Screencast

Screen.Recording.2025-01-01.at.15.35.12.mov

Screen.Recording.2025-01-01.at.15.36.33.mov

Screen.Recording.2025-01-01.at.15.38.17.mov

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Co-authored-by: himanshupathak95 <[email protected]>
Co-authored-by: t-hamano <[email protected]>

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[t-hamano]

LGTM!

• Could you rebase this PR to make sure it passes Check Storybook build on CI for PRs #68466?
• We should be able to remove this mixin.

[himanshupathak95]

Hi @t-hamano, Thanks for approving the PR.

✅ The storybook builds are successful

• We should be able to remove this mixin.

I will remove this in a follow-up PR which I am going to raise for this

This PR is ready to be merged now 🚀

[t-hamano]

@himanshupathak95 Thanks for the update!

• We should be able to remove this mixin.

I will remove this in a follow-up PR which I am going to raise for this

Is there any reason not to address this in this PR? If we don't remove this code in this PR, we will end up with redundant code like this:

.editor-post-featured-image__actions {
	&:not(.editor-post-featured-image__actions-missing-image) {
		@include reduce-motion("transition");

		@media not (prefers-reduced-motion) {
			transition: opacity 50ms ease-out;
		}
	}
}

[himanshupathak95]

@t-hamano, Thanks for the suggestion. I have removed the redundant mixin.