Feat: Add uniform image sizes toggle to Gallery Block

[yogeshbhutkar]

What, Why & How?

Adds support for maintaining uniform image sizes in gallery blocks, preventing the last image in a row from expanding to full width when there are fewer images than columns.

• Added new has-uniform-image-sizes class support.
• Used flex properties to maintain consistent image widths.
• Prevented image growth using flex: 0 0 width.
• Maintained existing gap calculations.
• Preserved default column behavior when uniform sizing is disabled.

Testing Instructions

1. Create a Gallery Block.
2. Add 4 Image Blocks to it.
3. Set the column count to 3.
4. Notice, by default the last image occupies the full width.
5. Try toggling the control labeled uniform image sizes and notice all the image blocks now take the same sizes.

Screencast

Closes: #68563

[github-actions]

Warning: Type of PR label mismatch

To merge this PR, it requires exactly 1 label indicating the type of PR. Other labels are optional and not being checked here.

• Type-related labels to choose from: [Type] Automated Testing, [Type] Breaking Change, [Type] Bug, [Type] Build Tooling, [Type] Code Quality, [Type] Copy, [Type] Developer Documentation, [Type] Enhancement, [Type] Experimental, [Type] Feature, [Type] New API, [Type] Task, [Type] Technical Prototype, [Type] Performance, [Type] Project Management, [Type] Regression, [Type] Security, [Type] WP Core Ticket, Backport from WordPress Core, Gutenberg Plugin.
• Labels found: .

Read more about Type labels in Gutenberg. Don't worry if you don't have the required permissions to add labels; the PR reviewer should be able to help with the task.

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: yogeshbhutkar <[email protected]>
Co-authored-by: jartes <[email protected]>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[yogeshbhutkar]

The feature implementation is complete. I will update the test cases after the initial round of review.