feat: posts block improvements

[HardeepAsrani]

Closes https://github.com/Codeinwp/otter-internals/issues/220.

Summary

• Change default block style to Boxed
• Change default heading to h4
• Change the default color, border, and number of posts

Screenshots

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Test instructions

• Confirm all the described changes
• Most importantly, make sure the default style of new block is Boxed but it shouldn't affect existing blocks.

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Checklist before the final review

• Included E2E or unit tests for the changes in this PR.
• Visual elements are not affected by independent changes.
• It is at least compatible with the minimum WordPress version.
• It loads additional script in frontend only if it is required.
• Does not impact the Core Web Vitals.
• In case of deprecation, old blocks are safely migrated.
• It is usable in Widgets and FSE.
• Copy/Paste is working if the attributes are modified.
• PR is following the best practices

[pirate-bot]

Plugin build for 252b3ab is ready 🛎️!

• Download Otter – Page Builder Blocks & Extensions for Gutenberg - Production ~ Development
• Download Otter Pro - Production ~ Development
• Download Blocks Animation - Production ~ Development
• Download Blocks CSS - Production ~ Development
• Download Blocks Export Import - Production ~ Development

[pirate-bot]

E2E Tests

Playwright Test Status:

Performance Results

serverResponse: 232.35, firstPaint: 158.8, domContentLoaded: 1569.8, loaded: 1570.3, firstContentfulPaint: 3447.85, firstBlock: 7627.85, type: 12.14, minType: 10.29, maxType: 15.87, typeContainer: 8.65, minTypeContainer: 7.43, maxTypeContainer: 10.47, focus: 31.72, minFocus: 27.66, maxFocus: 34.76, inserterOpen: 22.75, minInserterOpen: 19.74, maxInserterOpen: 36.89, inserterSearch: 0.7, minInserterSearch: 0.61, maxInserterSearch: 0.88, inserterHover: 2.87, minInserterHover: 2.53, maxInserterHover: 3.73, listViewOpen: 143.39, minListViewOpen: 132.78, maxListViewOpen: 159.57

[pirate-bot]

Bundle Size Diff

Package	Old Size	New Size	Diff
Animations	263.53 KB	263.53 KB	0 B (0.00%)
Blocks	1.51 MB	1.51 MB	230 B (0.01%)
CSS	93.23 KB	93.23 KB	0 B (0.00%)
Dashboard	196.5 KB	196.5 KB	0 B (0.00%)
Onboarding	153.19 KB	153.19 KB	0 B (0.00%)
Export Import	90.25 KB	90.25 KB	0 B (0.00%)
Pro	365.23 KB	365.23 KB	0 B (0.00%)

[pirate-bot]

🎉 This PR is included in version 3.0.0 🎉

The release is available on GitHub release

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